FN ISI Export Format VR 1.0 PT J AU Gebele, O Bohm, M Krey, U Krompiewski, S TI Systematic two-band model calculations of the GMR effect with metallic and non-metallic spacers and with impurities SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB By a semi-empirical Green's function method we calculate resistances and the corresponding giant magneto-resistance effects (GMR) of two metallic ferromagnetic films separated by different spacers, metallic and non-metallic ones, in a simplified model on an SC lattice, in CPP and CIP geometries (i.e. current perpendicular or parallel to the planes), without impurities, or with interface- or bulk impurities. The electronic structure of the systems is approximated by two hybridized orbitals per atom, to mimic s-bands and d-bands and their hybridization. We show that such calculations usually give rough estimates only, but of the correct order of magnitude; in particular, the predictions on the impurity effects depend strongly on the model parameters. One of our main results is the prediction of huge CPP-GMR effects for non- metallic spacers in the ballistic limit. (C) 2000 Elsevier Science B.V. All rights reserved. TC 0 BP 309 EP 326 PG 18 JI J. Magn. Magn. Mater. PY 2000 PD JUN VL 214 IS 3 GA 317ZW J9 J MAGN MAGN MATER UT ISI:000087259500020 ER PT J AU Hunziker, M Landolt, M TI Molecular-orbital model of heat-induced effective exchange coupling in magnetic multilayers SO PHYSICAL REVIEW LETTERS AB Heat-induced effective exchange coupling between two ferromagnets across a semiconductor spacer layer is described by the interaction of localized, weakly bound electron states which are situated at the two interfaces. These states overlap across the spacer layer and form large molecular orbitals. The energies of these orbitals depend on the spin configuration of the electrons and therefore determine the exchange coupling. Thermal repopulation of the levels yields a positive temperature coefficient of the coupling. The results are found to well reproduce the experimental observations. TC 0 BP 4713 EP 4716 PG 4 JI Phys. Rev. Lett. PY 2000 PD MAY 15 VL 84 IS 20 GA 313JT J9 PHYS REV LETT UT ISI:000086997100050 ER PT J AU Schleberger, M TI Quantitative investigation of amorphous Fe/Ge and Fe/Si by inelastic peak shape analysis SO SURFACE SCIENCE AB We investigate the nanostructure of amorphous iron/silicon and iron/germanium samples with inelastic background analysis of X- ray photoelectron spectra. To this end we deposit iron films of Varying thickness on amorphous silicon and germanium substrates. Additionally, we prepare codeposited iron-silicon and iron-germanium samples with varying stoichiometry. We show the interpolation of the inelastic mean free path from the corresponding values of the respective materials to be a valid approximation. We find that the Universal cross-section is fully sufficient for the analysis of iron/silicon and iron/germanium systems. The analysis of the nanostructure can be performed either with pure iron reference spectra or with coevaporated reference spectra. From the analysis of the Ge LMM and Si KLL substrate spectra we obtain only limited information for the thinner films. The analysis of the Fe 3p spectra from the deposits results in the quantitative determination of the nanostructure of our samples. (C) 2000 Elsevier Science B.V. All rights reserved. TC 0 BP 71 EP 79 PG 9 JI Surf. Sci. PY 2000 PD JAN 10 VL 445 IS 1 GA 275ZK J9 SURFACE SCI UT ISI:000084850500018 ER PT J AU Schleberger, M Walser, P Hunziker, M Landolt, M TI Amorphous Fe-Si and Fe-Ge nanostructures quantitatively analyzed by x-ray-photoelectron spectroscopy SO PHYSICAL REVIEW B AB The subject of this paper is an x-ray-photoelectron spectroscopy investigation of amorphous Fe-Si and Fe-Ge nanostructures that have attracted interest because of their magnetic coupling properties. To this end we deposit Fe onto clean, amorphous Si and Ge substrates at room temperature and at 40 K, respectively. We take spectra of the Fe3p, Fe2p, and Si2p core Levels to determine possible chemical shifts. The results indicate a charge transfer from the Fe to the Si and Ge atoms at room temperature as well as at 40 K. Additionally, we record wide range spectra of the SiKLL, GeLMM, and the Fe2p peaks as well as spectra of Fe-Si, and Fe-Ge compounds, respectively. Analyzing the inelastic background of the peaks we quantitatively determine the nanostructure of the deposits. We can exclude the formation of sharp interfaces. Instead, we find evidence for the formation of an Fe-Si or Fe-Ge interface compound with a homogeneous composition. For magnetically investigated low-temperature prepared Fe/Si/Fe trilayers we show that the spacer layer is a pure semiconductor with a thickness that is reduced compared to the nominal value. [S0163-1829(99)02443-1]. TC 1 BP 14360 EP 14365 PG 6 JI Phys. Rev. B PY 1999 PD NOV 15 VL 60 IS 20 GA 261NP J9 PHYS REV B UT ISI:000084015500062 ER PT J AU Bruno, P TI Theory of interlayer exchange interactions in magnetic multilayers SO JOURNAL OF PHYSICS-CONDENSED MATTER AB This paper presents a review of the phenomenon of interlayer exchange coupling in magnetic multilayers. The emphasis is put on a pedagogical presentation of the mechanism of the phenomenon, which has been successfully explained in terms of a spin-dependent quantum confinement effect. The theoretical predictions are discussed in connection with corresponding experimental investigations. TC 0 BP 9403 EP 9419 PG 17 JI J. Phys.-Condes. Matter PY 1999 PD DEC 6 VL 11 IS 48 GA 265NW J9 J PHYS-CONDENS MATTER UT ISI:000084251100011 ER PT J AU Ihara, N Narushima, S Kijima, T Abeta, H Saito, T Shinagawa, K Tsushima, T TI Magnetic properties and magnetoresistance of granular evaporated Fe/Si films SO JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS AB Fe (3.4 Angstrom) and Si (6 Angstrom) are evaporated alternately onto silica substrates to realize a granular structure. The substrate temperature T-s during the evaporation is changed from 100 K to 623 K to vary the film structures. The specimens of T-s greater than or equal to room temperature (RT) are superparamagnetic at RT, which suggests a granular structure. Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing magnetic field H) for all specimens. It is thought that the negative MR is attributable to the granular structure. On the other hand, at 77 K a positive MR linear with H (not H-2) up to 50 kOe is observed for all specimens. The linear dependence on H of the positive MR may be due to the nonuniformity in the granular structure. The positive MR itself and the change of the sign of MR from negative to positive with decreasing temperature have not been observed in conventional granular systems such as Co- Ag and Co-Al-O. TC 0 BP 6272 EP 6281 PG 10 JI Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. PY 1999 PD NOV VL 38 IS 11 GA 261ZT J9 JPN J APPL PHYS PT 1 UT ISI:000084041800021 ER PT J AU Matsuyama, K Nishihata, K Komatsu, S Nozaki, Y TI Magnetic and electric properties of Sn-oxide/M (M=Fe, Ni, Co) multilayers. SO IEEE TRANSACTIONS ON MAGNETICS AB Magnetic and electronic properties of novel semiconductive- oxide/ferromagnet multilayers of Sn-oxide and ferromagnetic metals (Fe, Ni, Co), deposited with a multi-target rf magnetron sputtering system, were studied. Among the studied material systems, Co/Sn-oxide sustains well-defined layer structure and ferromagnetic property for the thinnest thickness of 1 nm, A thermionic CPP transport was observed in [Co(2 nm) /Sn-oxide (4 nm)](10), which activation energy was evaluated as 4.4x10(-3) erg from the thermal dependence of conductivity. Negative magnetoresistance was observed in two orthogonal directions of in-plane external fields, which confirms spin dependent transport in Sn-oxide thin film, The measured MR change is 0.6 % (Delta R = 0.8 Omega, R-s=140 Omega) at room temperature. TC 0 BP 2901 EP 2903 PG 3 JI IEEE Trans. Magn. PY 1999 PD SEP VL 35 IS 5 PN 1 GA 246EH J9 IEEE TRANS MAGN UT ISI:000083151100216 ER PT J AU Dekoster, J Degroote, S Meersschaut, J Moons, R Vantomme, A Bottyan, L Deak, L Szilagyi, E Nagy, DL Baron, AQR Langouche, G TI Interlayer exchange coupling, crystalline and magnetic structure in Fe/CsCl-FeSi multilayers grown by molecular beam epitaxy SO HYPERFINE INTERACTIONS AB Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe/FeSi multilayers are investigated. From conversion electron Mossbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange coupling is identified with magnetometry and synchrotron Mossbauer reflectometry. From the fits of the time spectrum and the resonant theta-2 theta scans a model for the sublayer magnetization of the multilayer is deduced. TC 0 BP 39 EP 48 PG 10 JI Hyperfine Interact. PY 1999 VL 121 IS 1-8 GA 236UP J9 HYPERFINE INTERACTIONS UT ISI:000082617800006 ER PT J AU Walser, P Hunziker, M Landolt, M TI Heat-induced effective exchange coupling in magnetic multilayers with semiconductors SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB Two ferromagnetic films separated by an amorphous semiconducting spacer layer are exchange coupled across the spacer. The coupling is reversibly temperature dependent with a positive temperature coefficient making such layered systems a 2-D realization of the concept of heat-induced magnetism. By studying ferromagentic Fe layers separated by amorphous Si, Ge, or ZnSe layers we explore the possibilities to generate such an effective exchange coupling and address the question of the mechanism responsible for it. (C) 1999 Elsevier Science B.V. All rights reserved. TC 0 BP 95 EP 109 PG 15 JI J. Magn. Magn. Mater. PY 1999 PD OCT VL 200 IS 1-3 GA 241DP J9 J MAGN MAGN MATER UT ISI:000082867700008 ER PT J AU Walser, P Hunziker, M Speck, T Landolt, M TI Heat-induced antiferromagnetic coupling in multilayers with ZnSe spacers SO PHYSICAL REVIEW B AB Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. As spacer material we use amorphous ZnSe which is a compound semiconductor and find heat- induced antiferromagnetic coupling in striking similarity to amorphous Si and Ge. In an Fe/alpha-ZnSe/Fe trilayer with spacer thickness between 18 Angstrom and 22 Angstrom the coupling is antiferromagnetic with a positive temperature coefficient. At slightly larger thicknesses between 22 Angstrom and 25 Angstrom we find a reversible transition from ferromagnetic coupling at low temperatures to antiferromagnetic coupling at higher temperatures upon heating. We discuss the reversibly heat-induced effective exchange coupling in terms of localized defect states in the band gap in the vicinity of the Fermi energy. [S0163-1829(99)04230-7]. TC 1 BP 4082 EP 4086 PG 5 JI Phys. Rev. B PY 1999 PD AUG 1 VL 60 IS 6 GA 226AA J9 PHYS REV B UT ISI:000081997100053 ER PT J AU Walser, P Landolt, M TI Heat-induced coupling in multilayers with semiconducting spacers SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. (C) 1999 Elsevier Science B.V. All rights reserved. TC 0 BP 412 EP 414 PG 3 JI J. Magn. Magn. Mater. PY 1999 PD JUN VL 199 GA 204TE J9 J MAGN MAGN MATER UT ISI:000080779600130 ER PT J AU Moroni, EG Wolf, W Hafner, J Podloucky, R TI Cohesive, structural, and electronic properties of Fe-Si compounds SO PHYSICAL REVIEW B AB Phase stability, structural, and electronic properties of iron silicides in the Fe3Si, FeSi, and FeSi2 compositions are investigated by first-principle density-functional calculations based on ultrasoft pseudopotentials and all-electron methods. Structural stabilization versus spin-polarization effects are discussed at the Fe3Si composition, while for epsilon-FeSi and beta-FeSi2 we investigate their structural properties and the corresponding semiconducting band properties. All the computed results are analyzed and compared to available experimental data. The stability of the bulk phases, the lattice parameters, the cohesive energies and magnetic properties are found to be in good agreement with experiment when using the generalized gradient approximations for the exchange-correlation functional. Density-functional calculations are unable to account for the small bulk modulus of epsilon-FeSi despite that the computed lattice constant and internal atomic positions coincide with the experimental results. Both full-potential and ultrasoft-pseudopotential methods confirm for beta-FeSi2 the indirect nature of the fundamental gap, which is attributed to a transition between Y to 0.6X Lambda being 30% smaller than the experimental gap. Ultrasoft pseudopotential calculations of Fe-Si magnetic phases and of various nonequilibrium metallic phases at the FeSi and FeSi2 composition are presented. These calculations provide nb initio information concerning the stabilization of metallic pseudomorphic phases via high pressures or epitaxy. [S0163-1829(99)05419-3]. TC 2 BP 12860 EP 12871 PG 12 JI Phys. Rev. B PY 1999 PD MAY 15 VL 59 IS 20 GA 200ZW J9 PHYS REV B UT ISI:000080571000025 ER PT J AU Miyoshi, T Matsui, T Tsuda, H Mabuchi, H Morii, K TI Magnetic and electric properties of Mn5Ge3/Ge nanostructured films SO JOURNAL OF APPLIED PHYSICS AB We have investigated the magnetic, electric, and structural properties of Mn5Ge3/Ge nanostructured films produced by solid- state reaction of Mn/Ge multilayered films. The films composed of strongly uniaxially oriented Mn5Ge3 and randomly oriented Ge were successfully produced. The average grain size of Mn5Ge3 considerably changed according to the discharging power (E) of the ion source: 15 nm for E = 25 W and 50 nm for E = 50 W. The temperature dependence of the conductivity for the E = 25 sample showed semiconductor-type behavior over all the temperature region. Whereas the E = 50 sample, the conduction type changed from a metallic type (low temperature) to a semiconductor type (high temperature) with the transition temperature T-TR = 360 K. We also observed the anomalous magnetic behavior of Mn5Ge3. We discuss these behaviors in conjunction with the microstructure of the annealed films. The possibility of the carrier-spin exchange interactions has also been studied. (C) 1999 American Institute of Physics. [S0021- 8979(99)22208-6]. TC 0 BP 5372 EP 5374 PG 3 JI J. Appl. Phys. PY 1999 PD APR 15 VL 85 IS 8 PN 2B GA 188NF J9 J APPL PHYS UT ISI:000079853500032 ER PT J AU Endo, Y Kikuchi, N Kitakami, O Shimada, Y TI Antiferromagnetic coupling in Co/Ge superlattices SO JOURNAL OF PHYSICS-CONDENSED MATTER AB We have investigated interlayer coupling of Co/Ge superlattices. The present experiments obviously show that the coupling changes from ferromagnetic (F) to antiferromagnetic (AF) and finally to non-coupling (N) with the increase of Ge layer thickness. This coupling behaviour, as a function of the spacer thickness, is very similar to that of Fe/Si superlattices, although the coupling strength is much smaller than the latter: namely, similar to 0.05 erg cm(-2) for Co/Ge and similar to 1.0 erg cm(-2) for Fe/Si. Precise structural characterization indicates that diffused spacers at Co/Ge interfaces are responsible for the AF coupling. The same coupling behaviour has also been observed in Co/non-magnetic Co-Ge superlattices, where interdiffusion at the interfaces is entirely suppressed. All these results clearly demonstrate that the interlayer coupling between neighbouring Co layers is mediated by non-magnetic Co-Ge spacers. TC 0 BP L133 EP L137 PG 5 JI J. Phys.-Condes. Matter PY 1999 PD APR 19 VL 11 IS 15 GA 189PL J9 J PHYS-CONDENS MATTER UT ISI:000079913700001 ER PT J AU Wang, JZ Li, BZ TI Interlayer exchange coupling between two ferromagnets with finite thickness separated by a nonmetallic spacer SO PHYSICAL REVIEW B-CONDENSED MATTER AB Interlayer exchange coupling (IEC) between two ferromagnets (FM's) separated by a nonmetallic spacer is analyzed theoretically within the free-electron approximation. Particular attention is paid to the influence of FM thickness d(FM) On IEC and the variation of Fermi energy with the alignment of two FM's. The results show that (I)d(FM) strongly influence the IEC such that, only when d(FM) is not large, the barrier height and molecular field are both small, the IEC may oscillate with the spacer thickness owing to the quantum-size effect; otherwise, the IEC does not oscillate, but exhibits an exponential behavior in most spacer thickness; (2) as an oscillatory function of d(FM) with multiple periods, the IEC has a negative nonoscillatory term, which will become zero when the molecular field is comparatively small; (3) the Fermi energy has little difference between the parallel and antiparallel alignments of the two FM's, which correlates with the IEC to some extent. Particularly, with the increasing of d(FM) this correlation becomes stronger. [S0163-1829(99)01409- 5]. TC 0 BP 6383 EP 6389 PG 7 JI Phys. Rev. B-Condens Matter PY 1999 PD MAR 1 VL 59 IS 9 GA 178EX J9 PHYS REV B-CONDENSED MATTER UT ISI:000079254300058 ER PT J AU Endo, Y Kitakami, O Shimada, Y TI Interlayer coupling in Fe/Fe1-xSix superlattices SO PHYSICAL REVIEW B-CONDENSED MATTER AB Interlayer coupling has been investigated for a series of Fe/Fe1-xSix (0.4 less than or equal to x less than or equal to 1.0) superlattices. The layer of Fe1-xSix in the lattices is ferromagnetic for x<0.5 and causes ferromagnetic coupling between Fe layers for all spacer thicknesses investigated here. As the Si content increases above x=0.5, the layer becomes nonmagnetic and simultaneously our current in the plane of the sample and current perpendicular to the sample plane measurements suggest that the spacer rapidly changes its conduction property from metallic to highly resistive. Variations of the interlayer magnetic coupling as a function of spacer layer thickness for the spacer compositions above x=0.5 are similar to each other; namely, with an increase of the spacer thickness the interlayer coupling is initially ferromagnetic, then antiferromagnetic, and finally becomes noncoupling. Moreover, the temperature dependence of the bilinear and biquadratic coupling constants, J(1)(T) and J(2)(T) which were obtained by numerical fitting, varies sensitively with x. Assuming that the conduction of the spacers ranges from metallic to insulating as x increases, all these coupling behaviors can be described qualitatively by the quantum interference model formalized by Bruno. Furthermore, we found that the coupling strength is enhanced dramatically with increase of x of Fe1-xSix. [S0163-1829(99)11405-X]. TC 7 BP 4279 EP 4286 PG 8 JI Phys. Rev. B-Condens Matter PY 1999 PD FEB 1 VL 59 IS 6 GA 168NP J9 PHYS REV B-CONDENSED MATTER UT ISI:000078699400048 ER PT J AU Heide, C Elliott, RJ Wingreen, NS TI Spin-polarized tunnel current in magnetic-layer systems and its relation to the interlayer exchange interaction SO PHYSICAL REVIEW B-CONDENSED MATTER AB The spin-polarized tunnel current and its connection to the interlayer exchange interaction is studied in ferromagnet- insulator-ferromagnet thin-film planar junctions out of equilibrium. Building on the nonequilibrium Keldysh formalism, it is possible to systematically include a contact interaction between localized spins and conduction electrons and extend previous treatments on spin currents and exchange interaction. In particular, a Landauer-type formula is derived for the spin current that explains the result found earlier [Schwabe, Wingreen, and Elliott, Phys. Rev. B 54, 12 953 (1996)] that the exchange interaction between the ferromagnetic slabs increases in proportion to the slab width. Furthermore, switching is shown to occur between parallel and antiparallel coupling of the slabs for different applied biases under feasible experimental conditions. [S0163-1829(99)08705-6]. TC 2 BP 4287 EP 4304 PG 18 JI Phys. Rev. B-Condens Matter PY 1999 PD FEB 1 VL 59 IS 6 GA 168NP J9 PHYS REV B-CONDENSED MATTER UT ISI:000078699400049 ER PT J AU Vavra, I Bydzovsky, J Svec, P Harvanka, M Derer, J Frait, Z Kambersky, V Lopusnik, R Visnovsky, S Kubena, J Holy, V TI Structural, electrical and magnetic properties of Fe/Si and Fe/FeSi multilayers SO ACTA PHYSICA SLOVACA AB Fe/Si and Fe/FeSi multilayers with various spacer layer thickness (0.8-2.0 nm) were prepared by magnetron sputtering. The detailed structural analysis performed by low angle X-ray scattering and cross-sectional TEM revealed the differences between the microstructure of both kinds of multilayers. Magnetic analysis showed that interlayer exchange coupling is present only in Fe/FeSi multilayers with spacer layer thickness around 1.7 nm. TC 0 BP 743 EP 746 PG 4 JI Acta Phys. Slovaca PY 1998 PD DEC VL 48 IS 6 GA 155XP J9 ACTA PHYS SLOVACA UT ISI:000077972000036 ER PT J AU Krompiewski, S Krey, U TI Tunneling conductance and interlayer exchange coupling of metallic magnetic trilayers decorated with additional ultra- thin nonmetallic spacers SO EUROPHYSICS LETTERS AB By a very accurate recursion method based on the Kubo formula we calculate tunneling conductances of systems consisting of a nonmagnetic metallic spacer (MS) sandwiched between two ferromagnets (F) with additional ultra-thin nonmetallic (NM) interface layers. These hybrid structures are attached to voltage contacts by semi-infinite ideal lead wires (LW). The problem is treated in a two-band tight-binding model with hybridization. Our main finding is that the low-resistivity spin electron channel depends on the energy barrier width of the nonmetallic layer, and that with an asymmetric placement of the NM interface layers one can get large positive or negative values of the giant magnetoresistance with current- perpendicular-to-plane. TC 5 BP 661 EP 667 PG 7 JI Europhys. Lett. PY 1998 PD DEC 1 VL 44 IS 5 GA 145CK J9 EUROPHYS LETT UT ISI:000077353300019 ER PT J AU Tong, LN Pan, MH Wu, J Wu, XS Du, J Lu, M Feng, D Zhai, HR Xia, H TI Magnetic and transport properties of sputtered Fe/Si multilayers SO EUROPEAN PHYSICAL JOURNAL B AB The structural, magnetic and transport properties of sputtered Fe/Si multilayers were studied. The analyses of the data of the X-ray diffraction, resistance and magnetic measurements show that heavy atomic interdiffusion between Fe and Si occurs, resulting in multilayers of different complicated structures according to different sublayer thicknesses. The nominal Fe layers in the multilayers generally consist of Fe layers doped with Si; ferromagnetic Fe-Si silicide layers and nonmagnetic Fe-Si silicide interface layers, while the nominal Si spacers turn out to be Fe-Si compound layers with additional amorphous Si sublayers only under the condition either t(Si) greater than or equal to 3 nm for the series [Fe(3 nm)/Si(t(Si))](30) or t(Fe) < 2 nm for the series [Fe(t(Fe))/Si(1.9 nm)](30) multilayers. A strong antiferromagnetic (AFM) coupling and negative magnetoresistance (MR) effect, about 1%, were observed only in multilayers with iron silicide spacers and disappeared when alpha-Si layers appear in the spacers. The dependences of MR on t(Si) and on bilayer numbers N resemble the dependence of AFM coupling. The increase of MR ratio with increasing N is mainly attributed to the improvement of AFM coupling for multilayers with N. The t(Fe) dependence of MR ratio is similar to that in metal/metal system with predominant bulk spin dependent scattering and is fitted by a phenomenological formula for GMR. At 77 K both the MR effect and saturation field H-s increase. All these facts suggest that the mechanisms of the AFM coupling and MR effect in sputtered Fe/Si multilayers are similar to those in metal/metal system. TC 0 BP 61 EP 66 PG 6 JI Eur. Phys. J. B PY 1998 PD SEP VL 5 IS 1 GA 131HP J9 EUR PHYS J B UT ISI:000076570400009 ER PT J AU Bottyan, L Dekoster, J Deak, L Baron, AQR Degroote, S Moons, R Nagy, DL Langouche, G TI Layer magnetization canting in Fe-57/FeSi multilayer observed by synchrotron Mossbauer reflectometry SO HYPERFINE INTERACTIONS AB Synchrotron Mossbauer reflectometry and GEMS results on a [Fe- 57(2.55 nm)/FeSi (1.57 nm)](10) multilayer (ML) on a Zerodur substrate are reported. CEMS spectra are satisfactorily fitted by alpha-Fe and an interface layer of random alpha-(Fe, Si) alloy of 20% of the 57Fe layer thickness on both sides of the individual Fe layers. Kerr loops show a fully compensated AF magnetic layer structure. Prompt X-ray reflectivity curves show the structural ML Bragg peak and Kiessig oscillations corresponding to a bilayer period and total film thickness of 4.12 and 41.2 nm, respectively. Grazing incidence nuclear resonant Theta-2 Theta scans and time spectra (E = 14.413 keV, lambda = 0.0860 nm) were recorded in different external magnetic fields (0 < B-ext < 0.95 T) perpendicular to the scattering plane. The lime integral delayed nuclear Theta-2 Theta scans reveal the magnetic ML period doubling. With increasing transversal external magnetic field, the antiferromagnetic ML Bragg peak disappears due to Fe layer magnetization canting, the extent of which is calculated from the fit of the time spectra and the Theta-2 Theta scans using an optical approach. In a weak external field the Fe layer magnetization directions are neither parallel with nor perpendicular to the external field. We suggest that the interlayer coupling in [Fe/FeSi](10) varies with the distance from the substrate and the ML consists of two magnetically distinct regions, being of ferromagnetic character near substrate and antiferromagnetic closer to the surface. TC 6 BP 295 EP 301 PG 7 JI Hyperfine Interact. PY 1998 VL 113 IS 1-4 GA 124CT J9 HYPERFINE INTERACTIONS UT ISI:000076164300021 ER PT J AU Perez, GT Salas, FH Morales, R Alvarez-Prado, LM Alameda, JM TI Short-range order effects in amorphous FexSi1-x/Si multilayers induced by preparation conditions SO JOURNAL DE PHYSIQUE IV AB Magnetic properties of compositionally modulated FexSi1-x/Si amorphous multilayers are reported. The concentration x was 0.68 less than or equal to x less than or equal to 0.82 for two nominal modulation lengths lambda of 4 and 8 fi. The samples were prepared by pulsating two-cathode sputtering. From SQUID magnetometry and transverse magneto-optic Kerr effect, we detected a noticeable decrease in both magnetization and relative reflectivity (delta=Delta R/R) as lambda increases from 4 to 8 Angstrom. Also, for a fixed value of x, it was found that both coercive field and in-plane uniaxial anisotropy constant decrease systematically for increasing lambda. The two pulses used in the preparation method causes slight chemical short range effects, altering also the magnetic properties by changing the number and nature of nearest neighbors of a given Fe atom. The above short-range effects are present even when no multilayer structure is detected by x-ray diffraction. TC 0 BP 175 EP 178 PG 4 JI J. Phys. IV PY 1998 PD JUN VL 8 IS P2 GA ZX533 J9 J PHYS IV UT ISI:000074526300042 ER PT J AU Endo, Y Kitakami, O Shimada, Y TI Temperature dependence of interlayer coupling in Fe/Si superlattices SO IEEE TRANSACTIONS ON MAGNETICS AB We have explored the temperature dependence of the interlayer coupling in Fe/Fe1-xSix superlattices (0.5 less than or equal to x less than or equal to 1). It is found that the Si content of the Fe1-xSix, spacer greatly affects the temperature dependence of the bilinear and biquadratic coupling constants. Neither the "thickness fluctuation" model nor the "loose" spin model proposed by Slonczewski give satisfactory explanations to the temperature-dependent interlayer coupling. Instead, the present experimental results for all spacer compositions can be reproduced very well by the quantum interference model. We discuss the experimental results based on the above interlayer coupling models. TC 4 BP 906 EP 908 PG 3 JI IEEE Trans. Magn. PY 1998 PD JUL VL 34 IS 4 PN 1 GA 101CP J9 IEEE TRANS MAGN UT ISI:000074852300028 ER PT J AU Saito, Y Inomata, K TI Biquadratic coupling contributions to the magnetoresistive curves in Fe/FeSi/Fe sandwiches with semiconductor like FeSi and metallic bcc FeSi spacers SO JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN AB Magnetoresistance was investigated in Fe/FeSi/Fe sandwiches with metallic bcc-and semiconductor like FeSi spacers prepared by an ultrahigh-vacuum magnetron sputtering system, enhanced with inductively coupled RF plasma. In the easy axis direction, MR curves at 298 K have a dip around the zero magnetic field for both Fe/FeSi/Fe sandwiches with semiconductor like FeSi and hcc metallic FeSi spacers. On the other hand, MR curves at 10 K exhibit a dip and no anomaly around the zero magnetic field for the Fe/bcc metallic FeSi/Fe and Fe/semiconductor like FeSi/Fe sandwiches, respectively. when the contribution of biquadratic coupling to interlayer exchange coupling is considered, these MR behaviors are well explained. These results support the interlayer exchange coupling model attributed to the biquadratic exchange coupling which outweighs the colinear term at a low temperature in Fe/FeSi multilayers. TC 1 BP 1138 EP 1141 PG 4 JI J. Phys. Soc. Jpn. PY 1998 PD APR VL 67 IS 4 GA ZK389 J9 J PHYS SOC JPN UT ISI:000073315800019 ER PT J AU Walser, P Schleberger, M Fuchs, P Landolt, M TI Heat induced antiferromagnetic coupling in multilayers with Ge spacers SO PHYSICAL REVIEW LETTERS AB We report on heat induced antiferromagnetic exchange coupling in a new system: ferromagnetic Fe films separated by a spacer of amorphous Ge. Antiferromagnetic coupling occurs at spacer thicknesses between 20 and 25 Angstrom. It exhibits a striking temperature dependence which has a positive temperature coefficient and is fully reversible in the temperature range between 40 and 230 K. Our findings about the importance of the interfaces support the interpretation that resonant tunneling through localized states in the gap of the spacer mediate the magnetic exchange. TC 11 BP 2217 EP 2220 PG 4 JI Phys. Rev. Lett. PY 1998 PD MAR 9 VL 80 IS 10 GA ZA636 J9 PHYS REV LETT UT ISI:000072385400048 ER PT J AU Endo, Y Kitakami, O Shimada, Y TI Measurement of perpendicular giant magnetoresistance of Fe/Si superlattices SO APPLIED PHYSICS LETTERS AB The superlattices Fe/Si exhibit an antiferromagnetic coupling for very thin Si layers and giant magnetoresistance (GMR) is observed accompanying this coupling. The GMR for these superlattices measured with a current in the plane of the sample (CIP-GMR) is usually less than 0.2%. Considering a shunt effect due to large resistivity of Si layers, we measured the GMR with a current perpendicular to the sample plane (CPP-GMR). The thickness and width of the electrodes for the CPP measurement were carefully designed so that the current is always homogeneous in the sample. As a result, CPP-GMR for these superlattices is found to be about 3-6 times larger than CIP-GMR. Although a careful design of the electrodes is needed for homogeneity of the current, the technique is much easier than the CPP measurement for metal/metal superlattices and expected to provide valuable information on the spin-dependent electron transport phenomena in the Fe/Si superlattices. (C) 1998 American Institute of Physics. TC 5 BP 495 EP 497 PG 3 JI Appl. Phys. Lett. PY 1998 PD JAN 26 VL 72 IS 4 GA YT563 J9 APPL PHYS LETT UT ISI:000071619600035 ER PT J AU Xia, K Zhang, WY Lu, M Zhai, HG TI Noncollinear interlayer coupling across a semiconductor spacer SO PHYSICAL REVIEW B-CONDENSED MATTER AB Based on the extended s-d exchange model. which includes both isotropic and anisotropic spin interactions between conduction electrons and local states, we have derived analytically the interlayer coupling across a semiconductor spacer with a general band structure. Both Heisenberg-type and Dzyaloshinski- Moriya (DM) - type Ruderman-Kittel-Kasuya-Yosida-like interlayer coupling are obtained as a result of spin-orbit interaction. The interlayer coupling decreases exponentially with spacer thickness and the oscillation period depends on the band structure and orientation of spacers. Our result is different from previous theory; in particular, the DM-type interlayer exchange coupling offers a natural explanation to the noncollinear alignment of neighboring ferromagnetic layers as were observed in recent experiments on magnetic- semiconductor multilayer structures. TC 1 BP 14901 EP 14904 PG 4 JI Phys. Rev. B-Condens Matter PY 1997 PD DEC 15 VL 56 IS 23 GA YM239 J9 PHYS REV B-CONDENSED MATTER UT ISI:000071043700009 ER PT J AU Klasges, R Carbone, C Eberhardt, W Pampuch, C Rader, O Kachel, T Gudat, W TI Formation of a ferromagnetic silicide at the Fe/Si(100) interface SO PHYSICAL REVIEW B-CONDENSED MATTER AB The interplay between magnetism and chemistry at the Fe/Si(100) interface has been examined by spin-and angle-resolved photoemission. A ferromagnetically ordered metallic silicide of similar to 20 Angstrom thickness is formed by deposition of Fe on Si at room temperature. This interface layer is ferromagnetic in-plane with a reduced spin polarization in comparison to bulk Fe. Its electronic structure indicates an Fe-rich composition close to Fe,Si. The Fe/Si and Si/Fe interface are inequivalent with respect to silicide formation and to the resulting magnetic properties. [S0163-1829(97)04142- 8]. TC 7 BP 10801 EP 10804 PG 4 JI Phys. Rev. B-Condens Matter PY 1997 PD NOV 1 VL 56 IS 17 GA YD476 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1997YD47600027 ER PT J AU AlvarezPrado, LM Perez, GT Morales, R Salas, FH Alameda, JM TI Perpendicular anisotropy detected by transversely biased initial susceptibility via the magneto-optic Kerr effect in FexSi1-x thin films and FexSi1-x/Si multilayers: Theory and experiment SO PHYSICAL REVIEW B-CONDENSED MATTER AB We studied experimentally and theoretically the perpendicular anisotropy and the stripe-domain structure in both FexSi1-x thin films and FexSi1-x/Si multilayers, the latter being in the low-modulation-length regime (0.4 nm 11 ML. In situ surface magneto-optic Ken effect measurements show that at room temperature the fct and bcc regions are ferromagnetic, while the fee region is nonferromagnetic with some magnetic live layers. All magnetizations are in-plane. Oxygen absorption experiments suggest that these live layers are at the Fe/Co interface. Low temperature growth Fe/Co(100) shows a Ken signal that increases linearly with d(Fe) and suggests that the magnetic moments for fee Fe and bcc Fe are the same. To further study the magnetic properties of the nonferromagnetic ''fcc'' phase, we used metastable fee Fe as a spacer layer between two Co layers. The Co/fcc Fe/Co on Cu(100) sandwiches exhibit ferromagnetic coupling, strong antiferromagnetic coupling (AFC) and weak AFC. An oscillation in the strong AFC was found by artificially lengthening the thickness range of the nonferromagnetic fee phase. (C) 1996 American Vacuum Society. TC 2 BP 3164 EP 3170 PG 7 JI J. Vac. Sci. Technol. B PY 1996 PD JUL-AUG VL 14 IS 4 GA VD931 J9 J VAC SCI TECHNOL B UT ISI:A1996VD93100123 ER PT J AU Baszynski, J Szymanski, B Tolinski, T TI Evidence of the oscillations in the interlayer coupling of co sublayers across Co-Zr amorphous-like spacers, from M(H) curves SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB The first observations of oscillatory interlayer coupling between Co layers across the amorphous-like spacer Co-Zr with period 16 Angstrom for a series of Co(similar to 30 Angstrom)/Zr(t Angstrom), where 3 < t < 30, superlattices is presented. The total roughness of the interface is about a few monolayers on average. The strength of the AF interlayer coupling is about 0.01 erg/cm(2) at the AF1 peak. TC 0 BP 79 EP 80 PG 2 JI J. Magn. Magn. Mater. PY 1996 PD APR VL 156 IS 1-3 GA UV358 J9 J MAGN MAGN MATER UT ISI:A1996UV35800035 ER PT J AU Kohlhepp, J denBroeder, FJA TI Magnetic coupling in sputtered Fe/Si-type multilayers SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB In HV-sputtered Fe100-xSix/Si100-yFey multilayers the antiferromagnetic coupling strength and the fraction of ferromagnetic coupling increases with decreasing temperature. The ferromagnetic component can be explained by bridging along grain boundaries or by an Fe percolation mechanism in the nonmagnetic interlayers. Recent speculations that the magnetic coupling across the FeSi spacers is mediated by thermal excitation of charge carriers are incompatible with our observations. TC 15 BP 261 EP 262 PG 2 JI J. Magn. Magn. Mater. PY 1996 PD APR VL 156 IS 1-3 GA UV358 J9 J MAGN MAGN MATER UT ISI:A1996UV35800109 ER PT J AU Takahashi, Y Inomata, K TI Effect of composite nonmagnetic spacer layer on exchange coupling in magnetic superlattices SO PHYSICAL REVIEW B-CONDENSED MATTER AB We calculate the exchange coupling between ferromagnetic layers in magnetic superlattices, in which a potential scattering layer is inserted in nonmagnetic spacer layers. The Green's- function method is used for the formulation of the exchange coupling in the system. The numerical results of the exchange coupling are obtained by varying the parameters of the potential scattering layer, i.e., the potential height and width. The potential barrier plays the role of a gate across which waves of electrons in nonmagnetic spacer layers propagate. It is shown from the numerical results that the Rudermann-Kittel-Kasuya-Yosida-like exchange coupling between two ferromagnetic layers is changed significantly with potential barrier properties, and that the transition from ferromagnetic to antiferromagnetic coupling or the reverse can be induced by changing the potential parameters under a definite structure of the superlattices. TC 2 BP 13705 EP 13709 PG 5 JI Phys. Rev. B-Condens Matter PY 1996 PD MAY 15 VL 53 IS 20 GA UN909 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1996UN90900070 ER PT J AU Wang, ZJ Wen, LS Chang, XR Gu, YS Tian, ZZ Xiao, JM TI Oscillatory magnetic interlayer exchange coupling in Fe-N/TiN multilayers SO APPLIED PHYSICS LETTERS AB The discovery of oscillatory interlayer exchange coupling in a new type of ceramic superlattice system Fe-N/TiN, is reported. The magnitude of the exchange coupling was found to oscillate with the thickness of the TiN spacer layer and Fe-N ferromagnetic layer with periods about 0.8 and 0.6 nm, respectively. (C) 1996 American Institute of Physics. TC 3 BP 2887 EP 2889 PG 3 JI Appl. Phys. Lett. PY 1996 PD MAY 13 VL 68 IS 20 GA UK569 J9 APPL PHYS LETT UT ISI:A1996UK56900039 ER PT J AU Kawakami, RK EscorciaAparicio, EJ Qiu, ZQ TI Magnetic coupling in Co/face-centered-cubic Fe/Co sandwiches SO JOURNAL OF APPLIED PHYSICS AB Ferromagnetic (FC) and antiferromagnetic coupling (AFC) of Co layers across a metastable fee Fe spacer layer has been observed. Room-temperature-grown Fe on Co/Cu(100) was chosen as a spacer layer because it exhibits three distinct structural and magnetic phases depending on the thickness range: fct and ferromagnetic (region I), fee and nonferromagnetic (region II), bcc and ferromagnetic (region III) (listed in order of increasing thickness). Co/Fe/Co sandwiches were grown on Cu(100) by molecular beam epitaxy with a base pressure of similar to 2x10(-10) Ton, and characterized by low-energy electron diffraction and reflection high-energy electron diffraction. The magnetic properties were studied in situ using surface magneto;optic Ken effect. Using a wedged Fe spacer layer, we investigated the magnetic coupling between Co films across many thicknesses of Fe. We found FC in region I, strong AFC at the boundary between regions I and II, and weak AFC in region II. We also studied the effect of just the Co overlayer on the metastable fee Fe. We find that Co/Fe/Cu(100) differs qualitatively from Fe/Co/Cu(100). Finally, we find an oscillation in the AFC with a periodicity of similar to 12 Angstrom by artificially increasing the thickness range of region II. (C) 1996 American Institute of Physics. TC 3 BP 4532 EP 4534 PG 3 JI J. Appl. Phys. PY 1996 PD APR 15 VL 79 IS 8 PN 2A GA UG877 J9 J APPL PHYS UT ISI:A1996UG87700014 ER PT J AU Shi, ZP Klein, BM TI Antiferromagnetic coupling in magnetic multilayers with a narrow gap semiconductor spacer SO JOURNAL OF APPLIED PHYSICS AB Antiferromagnetic (AF) coupling has been observed in sputtered Fe/Si multilayers at room temperature, with thin spacers (<20 Angstrom) which were claimed to be FeSi. To study the magnetic coupling in this system we extend the RKKY interaction approach to a temperature-dependent narrow gap semiconductor. The strong AF coupling at room temperature and weakly ferromagnetic (F) coupling at low temperatures observed in Fe/Si can be explained from this model. (C) 1996 American Institute of Physics. TC 3 BP 4776 EP 4778 PG 3 JI J. Appl. Phys. PY 1996 PD APR 15 VL 79 IS 8 PN 2A GA UG877 J9 J APPL PHYS UT ISI:A1996UG87700108 ER PT J AU deMelo, CARS TI Magnetic exchange coupling mediated by bound states SO JOURNAL OF APPLIED PHYSICS AB Usually indirect exchange coupling is mediated by unbound, noncorrelated intermediate states (RKKY-like mechanisms) or by unbound, correlated intermediate states (superexchange-like mechanisms). Here we investigate the possibility of indirect magnetic exchange coupling mediated by bound, correlated intermediate states. As a concrete example we study the magnetic coupling between two magnetic impurities embedded in a semiconductor matrix. The importance of long ranged attractive Coulomb interactions between electrons and holes is emphasized. This attraction leads to exciton bound states which act as mediators of the effective exchange interaction between the two impurities. The resulting exchange interaction presents strong temperature dependence and can be analyzed in terms of the symmetry of the internal wavefunction of the exciton bound states. Possible applications of these results may include recent experimental results on ferromagnetic metal- semiconductor multilayers. (C) 1996 American Institute of Physics. TC 0 BP 5412 EP 5414 PG 3 JI J. Appl. Phys. PY 1996 PD APR 15 VL 79 IS 8 PN 2A GA UG877 J9 J APPL PHYS UT ISI:A1996UG87700352 ER PT J AU Fullerton, EE Bader, SD TI Temperature-dependent biquadratic coupling in antiferromagnetically coupled Fe/FeSi multilayers SO PHYSICAL REVIEW B-CONDENSED MATTER AB Fe/FeSi multilayers are known to exhibit a strong antiferromagnetic interlayer coupling peak centered at a nominal FeSi spacer thickness of similar to 15+/-2 Angstrom at room temperature, and to develop remanence in the magnetic hysteresis loop upon cooling to similar to 100 K. An analysis of the hysteresis loops is found to require the inclusion of a temperature-dependent biquadratic (90 degrees coupling) in addition to the bilinear coupling term in the energetics. The temperature dependence of the Fe/FeSi multilayer coupling can then be understood in terms that are applicable to conventional metallic multilayer systems such as Fe/Cr. TC 28 BP 5112 EP 5115 PG 4 JI Phys. Rev. B-Condens Matter PY 1996 PD MAR 1 VL 53 IS 9 GA UA011 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1996UA01100020 ER PT J AU Chaiken, A Michel, RP Wall, MA TI Structure and magnetism of Fe/Si multilayers grown by ion-beam sputtering SO PHYSICAL REVIEW B-CONDENSED MATTER AB Ion-beam sputtering has been used to prepare Fe/Si multilayers on a variety of substrates and over a wide range of temperatures. Small-angle x-ray-diffraction and transmission electron microscopy experiments show that the layers are heavily intermixed although a composition gradient is maintained. When the spacer layer is an amorphous iron silicide, the magnetic properties of the multilayers are similar to those of bulk Fe. When the spacer layer is a crystalline silicide with the B2 or DO3 structure, the multilayers show antiferromagnetic interlayer coupling like that observed in ferromagnet/paramagnet multilayers such as Fe/Cr and Co/Cu. Depending on the substrate type and the growth temperature, the multilayers grow in either the (011) or (001) texture. The occurrence of the antiferromagnetic interlayer coupling is dependent on the crystallinity of the iron and iron silicide layers, but does not seem to be strongly affected by the perfection of the layering or the orientation of the film. Since the B2- and DO3-structure FexSi1-x compounds are known to be metallic, antiferromagnetic interlayer coupling in Fe/Si multilayers probably originates from the same quantum-well and Fermi surface effects as in Fe/Cr and Co/Cu multilayers. TC 44 BP 5518 EP 5529 PG 12 JI Phys. Rev. B-Condens Matter PY 1996 PD MAR 1 VL 53 IS 9 GA UA011 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1996UA01100077 ER PT J AU Saito, Y Inomata, K Yusu, K TI Transition from antiferromagnetic coupling to biquadratic coupling in Fe/FeSi multilayers SO JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS AB The detailed temperature dependence of interlayer exchange coupling in Fe/FeSi multilayers prepared by ion beam sputtering was investigated and compared with the data for Fe/Si multilayers. Significant differences between interlayer exchange coupling in Fe/FeSi and Fe/Si multilayers were observed. The coupling between Fe layers in Fe/FeSi multilayers showed a transition from antiferromagnetic to 90 degrees coupling with decreasing temperature. This was due to the strong temperature dependence of J(2) (biquadratic coupling), which outweighs that of J(1) (collinear coupling) at low temperatures. TC 10 BP L100 EP L103 PG 4 JI Jpn. J. Appl. Phys. Part 2 - Lett. PY 1996 PD JAN 15 VL 35 IS 1B GA TU369 J9 JPN J APPL PHYS PT 2 UT ISI:A1996TU36900011 ER PT J AU BACK, CH WEBER, W BISCHOF, A PESCIA, D ALLENSPACH, R TI PROBING OSCILLATORY EXCHANGE COUPLING WITH A PARAMAGNET SO PHYSICAL REVIEW B-CONDENSED MATTER AB A paramagnet is used to probe directly the exchange coupling emanating from a ferromagnetic specimen across a nonmagnetic spacer material by measuring the induced magnetic moment. The model structure to observe the oscillatory exchange field consists of a Cu(100) single crystal, a Co base layer, a Cu spacer, and fee Fe as the paramagnetic probe layer with large magnetic susceptibility. Spin-resolving techniques show that the magnetization of the paramagnet oscillates as a function of the thickness of the spacer as well as of the paramagnet. TC 3 BP 13114 EP 13117 PG 4 JI Phys. Rev. B-Condens Matter PY 1995 PD NOV 1 VL 52 IS 18 GA TD725 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995TD72500012 ER PT J AU BRUNO, P TI THEORY OF INTERLAYER MAGNETIC COUPLING SO PHYSICAL REVIEW B-CONDENSED MATTER TC 174 BP 411 EP 439 PG 29 JI Phys. Rev. B-Condens Matter PY 1995 PD JUL 1 VL 52 IS 1 GA RH930 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995RH93000066 ER PT J AU OCHI, CLC MAJLIS, N TI DAMPED RUDERMAN-KITTEL-KASUYA-YOSIDA INTERACTION AMONG LOCAL MAGNETIC-MOMENTS IN THE IMPURITY-BAND REGIME OF DOPED SEMICONDUCTORS SO PHYSICAL REVIEW B-CONDENSED MATTER TC 0 BP 14221 EP 14225 PG 5 JI Phys. Rev. B-Condens Matter PY 1995 PD MAY 15 VL 51 IS 20 GA RB213 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995RB21300033 ER PT J AU BRINER, B LANDOLT, M TI EXCHANGE-COUPLING ACROSS SIO SO ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER AB Strongly temperature-dependent ferromagnetic exchange coupling is observed between Fe films separated by an amorphous SiO barrier. Heating reversibly enhances the coupling strength which monotonically decreases with increasing SiO thickness. At T = 40 K the coupling disappears for d(SiO) approximate to 20 Angstrom whereas at room temperature it persists up to a barrier thickness of 60 Angstrom, The coupling strength J is determined by externally compensating the exchange field of samples grown on an antiferromagnetically biased Fe/Cr/Fe structure, It amounts to J approximate to 2 . 10(-6) J/m(2) for a sample with d(SiO) = 25 Angstrom at T = 300 K. As a tentative explanation we propose that impurity or defect states within the large mobility gap of SiO carry the magnetic interaction across the insulating barrier. TC 3 BP 459 EP 463 PG 5 JI Z. Phys. B-Condens. Mat. PY 1995 PD MAY VL 97 IS 3 GA RA157 J9 Z PHYS B-CONDENS MATTER UT ISI:A1995RA15700010 ER PT J AU INOMATA, K YUSU, K SAITO, Y TI INTERLAYER COUPLING AND MAGNETORESISTANCE IN FE-SI MULTILAYERS WITH SEMICONDUCTING SPACERS SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB Two different types of antiferromagnetic (AF) interlayer coupling as a function of Si layer thickness t(Si) were observed in a series of (2.6 nm Fe-t(Si) nm Si)(22) multilayers prepared by ion beam sputtering on thermally oxidized Si substrates. One AF coupling was observed around t(Si) = 1.2 nm at room temperature and changed into ferromagnetic (F) coupling at Low temperature. This phenomenon was ascribed to a narrow gap semiconductor with impurity states in the energy gap formed at the interface. The other AF coupling was observed for t(Si) thicker than 1.5 nm Si, with a minimum around t(Si) = 2.5 nm, which was almost temperature independent; this was attributed to the formation of an amorphous Si layer for the thicker Si layers. Negative magnetoresistance was observed in the multilayers with AF coupling, which had a similar temperature dependence to that of the AF coupling. TC 1 BP 41 EP 47 PG 7 JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol. PY 1995 PD APR VL 31 IS 1-2 GA QV619 J9 MATER SCI ENG B-SOLID STATE M UT ISI:A1995QV61900007 ER PT J AU BRINER, B RAMSPERGER, U LANDOLT, M TI HEAT-ACTIVATED MAGNETIC EXCHANGE COUPLING ACROSS GE BARRIERS AND GE/SI HETEROSTRUCTURES SO PHYSICAL REVIEW B-CONDENSED MATTER TC 8 BP 7303 EP 7306 PG 4 JI Phys. Rev. B-Condens Matter PY 1995 PD MAR 15 VL 51 IS 11 GA QP774 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995QP77400066 ER PT J AU LANDOLT, M BRINER, B TI EXCHANGE COUPLING IN MULTILAYERS WITH SEMICONDUCTORS SO APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING AB Intrinsic and heat-induced exchange coupling exists between ferromagnetic films separated by non-magnetic semiconducting spacer layers. Magnetic coupling across thin amorphous layers of Si, SiO, Ge and Ge/Si heterostructures is described. Antiferromagnetic coupling occurs in a limited thickness range for Si and Si/Ge heterostructures, and ferromagnetic coupling is found for SiO, Ge, and certain thicknesses of Si and Si/Ge heterostructures. The coupling strength is very weak, of the order of a few 10(-6) J/m(2). It exhibits a pronounced temperature dependence with a positive temperature coefficient for both ferro- and antiferromagnetic couplings. The observations indicate that resonant tunneling through defect states in the spacer material mediates the exchange coupling. TC 2 BP 403 EP 409 PG 7 JI Appl. Phys. A-Mater. Sci. Process. PY 1995 PD APR VL 60 IS 4 GA QR568 J9 APPL PHYS A-MAT SCI PROCESS UT ISI:A1995QR56800009 ER PT J AU DEMELO, CARS TI MAGNETIC EXCHANGE COUPLING MEDIATED BY BOUND-STATES SO PHYSICAL REVIEW B-CONDENSED MATTER TC 5 BP 8922 EP 8927 PG 6 JI Phys. Rev. B-Condens Matter PY 1995 PD APR 1 VL 51 IS 14 GA QT246 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995QT24600027 ER PT J AU SHI, ZP SINGH, RRP KLEIN, BM TI INTERLAYER MAGNETIC COUPLING IN MAGNETIC KONDO-LATTICE MULTILAYERED STRUCTURES SO EUROPHYSICS LETTERS AB We study the interlayer coupling between metallic ferromagnetic materials, separated by a thin insulator spacer, modelled as a Kondo insulator, in an attempt to understand the behavior of Fe/FeSi multilayered structures. We find that interlayer magnetic coupling is antiferromagnetic at large band filling and ferromagnetic at small band filling with only one change in sign as a function of electron density. This dependence of the coupling on the electron density is contrasted with the pure RKKY coupling that would arise in a simple metal. It gives a way of understanding the photoinduced antiferromagnetic interlayer coupling in Fe/FeSi superlattices seen in recent experiments. TC 8 BP 585 EP 590 PG 6 JI Europhys. Lett. PY 1995 PD MAR 1 VL 29 IS 7 GA QM477 J9 EUROPHYS LETT UT ISI:A1995QM47700013 ER PT J AU FERT, A GRUNBERG, P BARTHELEMY, A PETROFF, F ZINN, W TI LAYERED MAGNETIC-STRUCTURES - INTERLAYER EXCHANGE COUPLING AND GIANT MAGNETORESISTANCE SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB Since the discovery of antiferromagnetic type interlayer coupling in 1986 and of 'Giant Magnetoresistance' in 1988, numerous systems have been investigated. Here we give a critical review of the research on these phenomena and illustrate the development with some results from our groups in Orsay and Juelich. TC 47 BP 1 EP 8 PG 8 JI J. Magn. Magn. Mater. PY 1995 PD FEB VL 140 PN 1 GA QL736 J9 J MAGN MAGN MATER UT ISI:A1995QL73600003 ER PT J AU INOMATA, K YUSU, K SAITO, Y TI MAGNETORESISTANCE ASSOCIATED WITH ANTIFERROMAGNETIC INTERLAYER COUPLING SPACED BY A SEMICONDUCTOR IN FE/SI MULTILAYERS SO PHYSICAL REVIEW LETTERS TC 44 BP 1863 EP 1866 PG 4 JI Phys. Rev. Lett. PY 1995 PD MAR 6 VL 74 IS 10 GA QK075 J9 PHYS REV LETT UT ISI:A1995QK07500042 ER PT J AU LEE, BC CHANG, YC TI EFFECTIVE-MASS APPROACH TO THE RKKY INTERACTION IN MAGNETIC MULTILAYERS SO PHYSICAL REVIEW B-CONDENSED MATTER TC 10 BP 316 EP 325 PG 10 JI Phys. Rev. B-Condens Matter PY 1995 PD JAN 1 VL 51 IS 1 GA QB377 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1995QB37700041 ER PT J AU INOMATA, K YUSU, K SAITO, Y TI TWO DIFFERENT TYPES OF ANTIFERROMAGNETIC COUPLINGS AND MAGNETORESISTANCES IN FE/SI MULTILAYERS SO JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS AB Two different types of antiferromagnetic (AF) interlayer couplings as a function of Si layer thickness, t(Si), have been observed in a series of (2.6 nm Fe/t(Si) nm Si)(22) multilayers. One of the AF-couplings was observed at around t(Si)=1.2 nm at room temperature (RT) and changed to ferromagnetic (F) coupling at a low temperature. The other AF coupling was observed for tsi thicker than 1.5 nm With a minimum around t(Si)=2.5 nm, and was almost temperature independent. Negative magnetoresistance has been observed in the multilayers with the AF coupling, and has similar temperature dependence as that of the AF coupling. TC 13 BP L1670 EP L1672 PG 3 JI Jpn. J. Appl. Phys. Part 2 - Lett. PY 1994 PD DEC 1 VL 33 IS 12A GA PW607 J9 JPN J APPL PHYS PT 2 UT ISI:A1994PW60700009 ER PT J AU FOILES, CL FRANKLIN, MR LOLOEE, R TI STRUCTURE OF SPUTTERED FE/SI MULTILAYERS SO PHYSICAL REVIEW B-CONDENSED MATTER TC 8 BP 16070 EP 16073 PG 4 JI Phys. Rev. B-Condens Matter PY 1994 PD DEC 1 VL 50 IS 21 GA PV862 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1994PV86200067 ER PT J AU BRUNO, P TI RECENT PROGRESS IN THE THEORY OF INTERLAYER EXCHANGE COUPLING (INVITED) SO JOURNAL OF APPLIED PHYSICS TC 11 BP 6972 EP 6976 PG 5 JI J. Appl. Phys. PY 1994 PD NOV 15 VL 76 IS 10 PN 2 GA PT848 J9 J APPL PHYS UT ISI:A1994PT84800314 ER PT J AU ZHANG, SF TI EXCHANGE MAGNETIC COUPLING THROUGH NONMAGNETIC INSULATOR SPACERS (ABSTRACT) SO JOURNAL OF APPLIED PHYSICS TC 0 BP 6993 EP 6993 PG 1 JI J. Appl. Phys. PY 1994 PD NOV 15 VL 76 IS 10 PN 2 GA PT848 J9 J APPL PHYS UT ISI:A1994PT84800321 ER PT J AU BRINER, B LANDOLT, M TI THERMALLY ACTIVATED BILINEAR AND BIQUADRATIC EXCHANGE COUPLING ACROSS AMORPHOUS-SILICON SO EUROPHYSICS LETTERS AB Ferromagnetic Fe and Ni films separated by a spacer layer of amorphous Si evaporated at T = 40 K exhibit oscillatory exchange coupling. Two antiferromagnetic-coupling regions are found for Si thicknesses around 16 angstrom and around 45 angstrom with a range of ferromagnetic coupling at thicknesses between them. We also observed biquadratic coupling at the first crossover between ferro- and antiferromagnetic orientations. The small bilinear coupling strength of about 5.10(-6) J/m2 can reversibly be enhanced upon heating. Irreversible thermal annealing, on the other hand, generally reduces the coupling and in some cases even changes its sign. From the reversible and irreversible temperature dependences we infer that resonant tunnelling through defect states in the spacer material mediates the magnetic exchange. TC 9 BP 65 EP 70 PG 6 JI Europhys. Lett. PY 1994 PD OCT 1 VL 28 IS 1 GA PM400 J9 EUROPHYS LETT UT ISI:A1994PM40000012 ER PT J AU BRINER, B LANDOLT, M TI INTRINSIC AND HEAT-INDUCED EXCHANGE COUPLING THROUGH AMORPHOUS- SILICON SO PHYSICAL REVIEW LETTERS AB We show that ferromagnetic films separated by a spacer of amorphous Si are exchange coupled for Si thicknesses d(Si) less-than-or-equal-to 40 angstrom. For 14 angstrom < d(Si) < 22 angstrom we observe antiferromagnetic coupling. The coupling strength of approximately 5 X 10(-6) J/m2 is strongly temperature dependent with a positive temperature coefficient. We suggest that localized electronic defect states in the gap of amorphous Si mediate the exchange interaction. The particular coupling mechanism encountered here also works with noncrystalline ferromagnetic layers. TC 64 BP 340 EP 343 PG 4 JI Phys. Rev. Lett. PY 1994 PD JUL 11 VL 73 IS 2 GA NW184 J9 PHYS REV LETT UT ISI:A1994NW18400031 ER PT J AU BRUNO, P TI THEORY OF INTRINSIC AND THERMALLY-INDUCED INTERLAYER MAGNETIC COUPLING BETWEEN FERROMAGNETIC-FILMS SEPARATED BY AN INSULATING LAYER SO PHYSICAL REVIEW B-CONDENSED MATTER AB A formalism developed previously to study the interlayer exchange coupling between ferromagnetic layers separated by a nonmagnetic metal spacer is applied to the case of an insulating spacer. It allows a unified treatment of both cases (metal and nonmetal spacer), provided one introduces the concept of a complex Fermi surface. In contrast to the metal- spacer case, where the exchange coupling decreases with increasing temperature, the coupling across an insulating spacer is found to increase with temperature. This finding is in agreement with recent experimental observations. TC 36 BP 13231 EP 13234 PG 4 JI Phys. Rev. B-Condens Matter PY 1994 PD MAY 1 VL 49 IS 18 GA NM433 J9 PHYS REV B-CONDENSED MATTER UT ISI:A1994NM43300105 ER PT J AU MATTSON, JE FULLERTON, EE KUMAR, S LEE, SR SOWERS, CH GRIMSDITCH, M BADER, SD PARKER, FT TI PHOTOINDUCED ANTIFERROMAGNETIC INTERLAYER COUPLING IN FE SUPERLATTICES WITH IRON SILICIDE SPACERS SO JOURNAL OF APPLIED PHYSICS AB Sputtered Fe/FeSi films possessing antiferromagnetic (AF) interlayer coupling at room temperature develop ferromagnetic remanence when cooled below 100 K, but the AF coupling can be restored at low temperature by exposure to visible light of sufficient intensity (> 10 mW/mm2). We attribute these effects to charge carriers in the FeSi spacer layer, which, when thermally or photogenerated, are capable of communicating spin information between the Fe layers. TC 5 BP 6169 EP 6173 PG 5 JI J. Appl. Phys. PY 1994 PD MAY 15 VL 75 IS 10 PN 2A GA NN734 J9 J APPL PHYS UT ISI:A1994NN73400261 ER PT J AU SIEGMANN, HC TI SURFACE AND 2D MAGNETISM WITH SPIN-POLARIZED CASCADE ELECTRONS SO SURFACE SCIENCE AB The probing depth lambda of low energy cascade electrons in transition metals (TM) is dominated by scattering into the unoccupied d-orbitals. Thus lambda for electrons within 5-10 eV from the Fermi level varies from 1 monolayer in the early TM such as Gd to 6 monolayers in the late TM(Ni). The spin polarization P(c) of the cascade electrons is due to the spin polarization P0 of the 3d-electrons plus an additional polarization generated in the process of cascade formation by scattering into the spin polarized holes of the 3d-states. The enhancement f = P(c)/P0 is small with the early TM but large with the late TM. Nevertheless, P(c) is proportional to the magnetization and therefore represents an ideal tool to observe magnetism at surfaces and in nanoscale magnetic structures. Very small exchange couplings of ferromagnets across nonmagnetic spacer layers can be measured if one of the ferromagnets is ultrathin and acts as a giant spin molecule without decaying into domains. Recent applications include the investigation of the exchange coupling across semiconducting spacer layers. TC 0 BP 1076 EP 1086 PG 11 JI Surf. Sci. PY 1994 PD APR 20 VL 309 PN B GA NH823 J9 SURFACE SCI UT ISI:A1994NH82300079 ER PT J AU MUNOZ, MC PEREZDIAZ, JL TI EXCHANGE COUPLING IN MAGNETIC MULTILAYERS - A QUANTUM-SIZE EFFECT SO PHYSICAL REVIEW LETTERS AB The long-wavelength oscillations observed in magnetic multilayers axe explained by an indirect Ruderman-Kittel- Kasuya-Yosida-like (RKKY) exchange interaction. A perturbative theory of the RKKY-like exchange coupling between two ferromagnetic layers separated by a nonmagnetic slab is derived. The approach includes a realistic description of the multilayer one-electron states, whose wave functions satisfy matching conditions at the ferromagnetic-nonmagnetic interfaces. The quantum-size effects exhibited by the electron transmission coefficient give rise to a distinct multilayer wavelength lambda. which provides the measured long periods. TC 28 BP 2482 EP 2485 PG 4 JI Phys. Rev. Lett. PY 1994 PD APR 11 VL 72 IS 15 GA NE851 J9 PHYS REV LETT UT ISI:A1994NE85100044 ER PT J AU HOMMA, H ANKER, JF MAJKRZAK, CF TI MAGNETIC DEPTH PROFILES OF MAGNETIC MULTILAYERS FE/SI AND FE/W USING POLARIZED NEUTRON REFLECTOMETRY SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB We have studied the magnetic properties and roughness at interfaces of sputtered magnetic multilayers Fe/Si and Fe/W, employing a newly developed magnetic profile refinement program for polarized neutron reflectivity data. This modeling demonstrates the capability to measure magnetic moment depth profiles near interfaces quantitatively. TC 1 BP 257 EP 260 PG 4 JI J. Magn. Magn. Mater. PY 1993 PD SEP VL 126 IS 1-3 GA MD354 J9 J MAGN MAGN MATER UT ISI:A1993MD35400069 ER PT J AU BRINER, B LANDOLT, M TI LIGHT-INDUCED MAGNETIC EXCHANGE-COUPLING SO ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER AB We observe ferromagnetic exchange-coupling to be induced between thin Fe layers separated by an insulating SiO barrier upon light irradiation. Coupling can reversibly be switched on with photons of energies less than the bandgap of SiO. We conclude that charge carriers in localized states within the bandgap mediate the observed exchange-coupling. We furthermore report that the exchange-coupling can also be turned off by irradiation with light of higher intensity. TC 14 BP 137 EP 139 PG 3 JI Z. Phys. B-Condens. Mat. PY 1993 PD OCT VL 92 IS 2 GA LZ856 J9 Z PHYS B-CONDENS MATTER UT ISI:A1993LZ85600002 ER PT J AU MATTSON, JE KUMAR, S FULLERTON, EE LEE, SR SOWERS, CH GRIMSDITCH, M BADER, SD PARKER, FT TI PHOTOINDUCED ANTIFERROMAGNETIC INTERLAYER COUPLING IN FE/(FE- SI) SUPERLATTICES SO PHYSICAL REVIEW LETTERS AB We report photoinduced antiferromagnetic (AF) interlayer coupling in sputtered Fe/(Fe-Si) superlattices. The superlattices are intrinsically AF coupled at room temperature and become increasingly ferromagnetically coupled when cooled below 100 K, but the AF coupling is restored at low temperature by exposure to visible light of sufficient intensity ( > 10 mW/mm2). These effects are due to charge carriers in the Fe-Si spacer layer which, when thermally or optically generated, are capable of communicating spin information between the Fe layers. TC 73 BP 185 EP 188 PG 4 JI Phys. Rev. Lett. PY 1993 PD JUL 5 VL 71 IS 1 GA LK368 J9 PHYS REV LETT UT ISI:A1993LK36800048 ER PT J AU FULLERTON, EE MATTSON, JE LEE, SR SOWERS, CH HUANG, YY FELCHER, G BADER, SD PARKER, FT TI MAGNETIC DECOUPLING IN SPUTTERED FE/SI SUPERLATTICES AND MULTILAYERS SO JOURNAL OF APPLIED PHYSICS AB Sputtered Fe/Si superlattices were grown to study the magnetic coupling between ferromagnetic Fe layers (30 angstrom thick) for Si spacer-layer thicknesses (t(Si)) between 10 and 40 angstrom. The material is ferromagnetical for t(Si) < 13 angstrom and antiferromagnetically coupled for 13 angstrom < t(Si) < 17 angstrom. For t(Si) > 17 angstrom the Fe layers are uncoupled. X-ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for t(Si) < 17 angstrom. These results, along with our Mossbauer investigation, strongly suggest that the Si layer is crystalline for t(Si) < 17 angstrom, and is silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe silicide. TC 22 BP 6335 EP 6337 PG 3 JI J. Appl. Phys. PY 1993 PD MAY 15 VL 73 IS 10 PN 2B GA LD865 J9 J APPL PHYS UT ISI:A1993LD86500071 ER PT J AU ANKNER, JF MAJKRZAK, CF HOMMA, H TI MAGNETIC DEAD LAYER IN FE/SI MULTILAYER - PROFILE REFINEMENT OF POLARIZED NEUTRON REFLECTIVITY DATA SO JOURNAL OF APPLIED PHYSICS AB We have used polarized neutron reflectometry to study the magnetic structure of an Fe/Si multilayer film. By simultaneous refinement of both plus and minus reflectivities we have extracted separate nuclear and magnetic scattering density profiles that include a 6-angstrom-thick magnetically dead layer in Fe at the interface. This result supports the contention that the antiferromagnetic coupling reported in this system is mediated by the presence of Fe in the Si interlayers. TC 10 BP 6436 EP 6437 PG 2 JI J. Appl. Phys. PY 1993 PD MAY 15 VL 73 IS 10 PN 2B GA LD865 J9 J APPL PHYS UT ISI:A1993LD86500109 ER PT J AU FULLERTON, EE MATTSON, JE LEE, SR SOWERS, CH HUANG, YY FELCHER, G BADER, SD PARKER, FT TI NONOSCILLATORY ANTIFERROMAGNETIC COUPLING IN SPUTTERED FE/SI SUPERLATTICES SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB A series of sputtered Fe(30 angstrom)/Si(x) superlattices were grown for x = 10-40 angstrom. Magnetization and Kerr hysteresis loops, and neutron-reflectivity measurements identify antiferromagnetic (AF) coupling of the Fe layers at room temperature for x = 15 angstrom nominal thickness, with switching fields of 6 kOe. X-rav structural analyses indicate that the spacer medium is crystalline for k < 20 angstrom, while sputtered Si is amorphous (a). Failure to detect oscillations in the AF coupling for thicker Si layers is due to the formation of a-Si, as opposed to the crystalline silicide responsible for the coupling. TC 57 BP L301 EP L306 PG 6 JI J. Magn. Magn. Mater. PY 1992 PD DEC VL 117 IS 3 GA KE888 J9 J MAGN MAGN MATER UT ISI:A1992KE88800001 ER