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