SCI CDE with Abstracts (Jan 99 - Dec 99) (D4.1) Record 1 of 20. Title: Bilinear and Biquadratic Interlayer Exchange Coupling in Sputtered Co/Cu Multilayers Damaged with Residual-Gas Impurities Authors: Marrows-CH Hickey-BJ Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 1, pp 463-467 Abstract: The oscillatory indirect exchange coupling exhibited by magnetic/nonmagnetic metal multilayers is known to be highly sensitive to structural defects. We have measured the effects on coupling of residual gas atoms in sputtered Co/Cu multilayers. We have used a simple technique to selectively probe particular parts of the multilayer stack. A large reduction in the giant magnetoresistance has been observed when gas impurity atoms are introduced into the middle of the Cu spacer layers, with a corresponding increase in the remanence of the sample. These changes are shown to be consistent with overwhelmingly strong biquadratic coupling between the Co layers. This leads to the moments in adjacent layers being no longer collinear in zero applied field, which we have confirmed by other measurements. We discuss the applicability of the various theoretical models of biquadratic coupling to our observations. [S0163-1829(99)04901-2]. Record 2 of 20. Title: Giant Magnetoresistance and Oscillatory Exchange Coupling in Disordered Co/Cu Multilayers Authors: Marrows-CH Wiser-N Hickey-BJ Hase-TPA Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 1, pp 81-88 Abstract: We measured the exchange coupling strength and magnetoresistance for multilayers of Co/Cu grown by sputtering. The samples have (111) texture with a grain size of about 140 Angstrom. Their mosaic spread, determined by high-angle x-ray rocking curves in triple-axis geometry, is as large as 16 degrees, suggesting the description disordered. The magnetoresistance oscillates as a function of the Cu thickness and reaches 70% at room temperature with near zero remanence at the first antiferromagnetic peak. These results indicate that a sufficient condition for oscillatory exchange coupling with a period of similar to 10 Angstrom is a well defined separation between the magnetic layers. We also measured the exchange coupling strength as a function of the magnetic layer thickness and found no oscillations. The measured saturating magnetic field is accurately described by the 'orange-peel' coupling effect. Record 3 of 20. Title: Extraordinary Interlayer Coupling in Co/Cu(Mn) Multilayers Authors: Kobayashi-Y Aoki-Y Sato-H Loloee-R Pratt-WP Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 5, pp 3734-3739 Abstract: We have investigated the effect of Mn doping into Cu layers on the interlayer coupling in Co/Cu multilayers and found a partial change of the interlayer coupling from ferromagnetic to antiferromagnetic or vice versa with decreasing temperature. The change of the interlayer coupling occurs around a critical temperature which depends on both the Cu(Mn) layer thickness and Mn concentration. As an origin of the change of the interlayer coupling, a cooperative interaction among the Co layers and the Mn ions is discussed in correlation with a spin-glass-like state. [S0163-1829(99)06305-X]. Record 4 of 20. Title: Exchange Coupling in Co-Ti Layered Structures Authors: Smardz-L Full source: SOLID STATE COMMUNICATIONS 1999, Vol 112, Iss 12, pp 693-698 Abstract: The Co-Ti multilayers with constant thickness sublayers and Co-d(Ti)-Ti-Co trilayers with wedge-shaped Ti interlayers were prepared using an ultra high vacuum (5 x 10(-10) mbar) DC-RF magnetron sputtering. The planar growth of the Co and Ti sublayers was confirmed in situ by X-ray photoelectron spectroscopy. The Co sublayers grow in the soft magnetic nanocrystalline phase (with average grain size D << 10 nn) up to a critical thickness d(crit) similar to 3 nm. For a thickness greater than d(crit), the Co sublayers undergo a structural transition to the polycrystalline phase with D > 10 nm. Results show that the Co sublayers are very weakly exchange coupled or decoupled for d(Ti) > 2.7 nn. The rapid decrease of the interlayer exchange coupling could be explained by its strong damping due to the formation of a non-magnetic quasi-amorphous Co-Ti alloy layer at the interfaces. The nanocrystalline Co sublayers with d(Co) = 2.2 nm showed a weak 90 degrees coupling near the transition zone (d(Ti) similar to 2 nm) from ferromagnetic to week antiferromagnetic coupling. (C) 1999 Elsevier Science Ltd. All rights reserved. Record 5 of 20. Title: Inhomogeneous Ferromagnetic-Resonance Modes in (Fe/Cr)(N) Superlattices with a High Biquadratic Exchange Constant Authors: Drovosekov-AB Zhotikova-OV Kreines-NM Kholin-DI Meshcheryakov-VF Milyaev-MA Romashev-LN Ustinov-VV Full source: JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS 1999, Vol 89, Iss 5, pp 986-994 Abstract: In a set of [Fe/Cr](n) superlattices, magnetization curves and spectra of ferromagnetic resonance under an in-plane magnetic field have been studied at room temperature. Along with the acoustic branch, several additional branches have been observed in resonance spectra. Resonance spectra have been calculated analytically for a structure with an infinite number of layers and numerically for finite numbers of layers in real samples using a model of biquadratic exchange taking account of the fourth-order magnetic anisotropy. A possibility of describing both static and resonance properties of the system in terms of this model has been demonstrated. (C) 1999 American Institute of Physics. [S1063-7761(99)02311-2]. Record 6 of 20. Title: Effect of Biquadratic Exchange Coupling on Magnetoresistance and Magnetization Process in Magnetic Bilayer Systems Authors: Kuo-CC Lin-MT Huang-HL Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 4430-4432 Abstract: An improved model is proposed to deal with the magnetic bilayer systems taking into account the contribution of the anisotropy energy and biquadratic exchange coupling to elaborate on the evolution of the magnetoresistance (MR) ratio and magnetization process. The results indicate that the characteristic behavior of the MR ratio depends distinctly on both the biquadratic coupling constant and the layer thickness. The profile of the MR ratio was found to vary from an inverted bell shape to a concave pyramid with increasing biquadratic coupling strength, and decays sharply with the layer thickness. This model calculation helps us to provide a venue for further understanding the MR or giant magnetoresistance behavior of the magnetic multilayer system. (C) 1999 American Institute of Physics. [S0021-8979(99)48108-3]. Record 7 of 20. Title: Oscillations of the Curie-Temperature and Interlayer Exchange Coupling in Magnetic Trilayers Authors: Ney-A Wilhelm-F Farle-M Poulopoulos-P Srivastava-P Baberschke-K Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp R3938-R3940 Abstract: The onset of long-range magnetic order in exchange-coupled epitaxial Co/Cu/Ni trilayers, 2-4 monolayers (ML) each, on Cu(001) is studied by element-specific x-ray magnetic circular dichroism between 30 and 300 K in ultrahigh vacuum. Oscillations of the enhancement of the ordering temperature of Ni (Delta T (Ni)) by more than 40 K are measured as a function of interlayer exchange interaction by varying the Cu(001) spacer thickness. Below a Cu thickness of 2.3 ML antiferromagnetic coupling is measured. The period, phase, and amplitude of the Delta T (Ni) oscillations an in excellent agreement with the theoretical prediction for the short- and long-period oscillations of the interlayer exchange coupling. Record 8 of 20. Title: Interlayer Coupling in Fe/Fe1-Xsix Superlattices Authors: Endo-Y Kitakami-O Shimada-Y Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4279-4286 Abstract: 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]. Record 9 of 20. Title: Magnetic Effect in Multilayer Fe/Cr Films Authors: Santos-VC Fernandes-AAR Full source: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 1999, Vol 10, Iss 1, pp 67-70 Abstract: Ferromagnetic resonance measurements on different Fe/Cr multilayer samples with the same thickness of the spacing Cr layers suggest that these multilayers have a different magnetic behavior depending on the thickness of the active Fe layers. In this work we show that the change of magnetic behavior from bulk mode to surface mode is observed only when the thickness of the Fe layers is less than 4 nm. This is attributed to the Fe layer thickness and to the relative thickness of the magnetic and non-magnetic layers. (C) 1999 Kluwer Academic Publishers. Record 10 of 20. Title: Electrical-Transport in Metallic Thin-Films for Giant Magnetoresistance Modeling Purposes Authors: Persat-N Vandenberg-HAM Dinia-A Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 89-91 Abstract: A method is presented to determine the mean free path in individual layers of giant magnetoresistive samples from experimental data. The boundary conditions at the surfaces of the thin films are fixed at certain positions within the stack by the implementation of foreign atoms. The scattering activities of these atoms are analysed by means of the GMR response of specially designed samples. An analytical expression is used to model the variation of the sheet conductance as a function of the thickness of Cu and Co thin sputtered films. The data of Cu are well reproduced by means of a single bulk mean free path, whereas for Co, a spin dependence of the mean free paths is needed. (C) 1999 Elsevier Science B.V. All rights reserved. Record 11 of 20. Title: Evolution of Microstructure and Magnetoresistance in Co/Cu Multilayers During Annealing Authors: Ratzke-K Hall-MJ Jardine-DB Shih-WC Somekh-RE Greer-AL Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 204, Iss 1-2, pp 61-67 Abstract: Co/Cu multilayers [Co (1.5 nm)/Cu (4 nm)](35) made by magnetron sputtering have been investigated by vibrating-sample magnetometry, electrical resistance measurements and low-angle X-ray diffractometry before and after annealing at 275 degrees C < T < 350 degrees C for selected times. The observed changes in electrical and magnetic properties are small and consistent with a break-up of the Co layers by diffusion of Cu along the grain boundaries within them. The study of the early stages of break-up is facilitated by choosing layer thicknesses greater than would be optimal for GMR. (C) 1999 Elsevier Science B.V. All rights reserved. Record 12 of 20. Title: Suppression of the Face-Centered-Cubic-Hexagonal-Close-Packed Stacking-Fault in Co/Cu(111) Ultrathin Films by Pulsed-Laser Deposition Authors: Zheng-M Shen-J Mohan-CV Ohresser-P Barthel-J Kirschner-J Full source: APPLIED PHYSICS LETTERS 1999, Vol 74, Iss 3, pp 425-427 Abstract: The thermal deposition of Co onto Cu(111) results in three-dimensional island growth and a face-centered-cubic-hexagonal-close-packed stacking fault, which hinders a complete antiferromagnetic coupling in Co/Cu(111) superlattices. We report that Co/Cu(111) films can be grown with good layer-by-layer morphology and significantly less stacking faults by pulsed laser deposition. We show that a complete antiferromagnetic coupling can be achieved in the pulsed laser deposited Co/Cu trilayer. (C) 1999 American Institute of Physics. [S0003-6951(99)02003-3]. Record 13 of 20. Title: Structure and Annealing of Nimn Spin Valves Authors: Loch-C Maass-W Ocker-B Rooll-K Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 4460-4462 Abstract: The thermal stability of sputtered NiMn pinned spin valves (NiFe/Co/Cu/Co/NiFe/NiMn) was studied for different Co and Cu thicknesses. The coupling between NiFe and antiferromagnetic NiMn was established by an annealing process which also led to a change of magnetoresistance due to diffusion through the Cu layer. Annealing was performed under vacuum in a magnetic field to prevent degradation of the magnetic anisotropy in the antiferromagnet. High angle x-ray diffraction showed a typical shift of the (111) NiMn peak during annealing and a structural change with different Co thicknesses. (C) 1999 American Institute of Physics. [S0021-8979(99)34808-8]. Record 14 of 20. Title: A New Process to Manufacture Thin SiGe and Sigec Epitaxial-Films on Silicon by Ion-Implantation and Excimer-Laser Annealing Authors: Boher-P Stehle-JL Fogarassy-E Full source: APPLIED SURFACE SCIENCE 1999, Vol 139, Iss JAN, pp 199-205 Abstract: Epitaxial Si1-yCy and Si1-x-yGexCy alloy layers are grown on monocrystalline silicon substrates by multiple energy ion implantation of Ge and C into single Si crystals followed by pulse excimer laser annealing. The properties of the alloy layers are determined precisely using spectroscopic ellipsometry (SE), X-ray diffraction (XRD) and Rutherford backscattering (RBS) techniques. We show that annealing energy densities higher than 2 J/cm(2) result in monocrystalline epitaxial layers with low quantity of defects. The lattice contraction due to the carbon inclusion increases with the implanted C concentration up to about 1.1%. For higher values a more complex behavior is observed with partial (or total) relaxation of the layer and/or carbide formation. With optimized condition, the growing of pseudomorphic epitaxial layers, from group IV semiconductor alloys was successful on large areas (1 J/cm(2) over 40 cm(2) in one pulse). (C) 1999 Elsevier Science B.V. All rights reserved. Record 15 of 20. Title: Atomic-Structure of (112)Sigma=3 Twin Boundary in Beta-SiC Authors: Ragaru-C Lancin-M Godon-C Full source: EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS 1999, Vol 5, Iss 2, pp 135-141 Abstract: We study the atomic structure of {112}Sigma = 3 twirl boundaries consisting of a stacking of six {111} planes and characterized by a resulting Burger vector equal to zero. The twins were imaged by HRTEM. We develop image processing to localize the silicon and carbon atoms in each grain and thus to deduce their stacking and to calculate the possible rotation and translation of one grain with respect tu the other with an accuracy greater than 0.1%. We show that there is no rigid body translation between the two grains. However, models derived from Moller or Pond ct al, are not suitable. We propose an alternative model which is in close agreement with the asymmetrical contrast of the twirl boundary. Record 16 of 20. Title: Direct Experimental-Study of the Microscopic Remagnetization Mechanism in Co Cu Magnetic Superlattices Authors: Nikitenko-VI Gornakov-VS Dedukh-LM Khapikov-AF Moffat-TP Shapiro-AJ Shull-RD Shima-M Salamancariba-L Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 477-479 Abstract: Using the magneto-optical indicator film technique, the correlation between the magnitude of the giant magnetoresistance (GMR) and the micromechanism of the magnetization reversal of electrodeposited Co/Cu superlattices are investigated for a range of Cu spacer thicknesses. The multilayers showing vanishing GMR exhibit a cooperative spin behaviour, which is similar to that exhibited by thin ferromagnetic films with in-plane fourfold anisotropy. Tn contrast, superlattices with a substantial GMR demonstrate partially coupled noncollinear spin configurations, which are probably responsible for the observed giant magnetoresistance phenomenon. (C) 1999 Elsevier Science B.V. All rights reserved. Record 17 of 20. Title: Crystallization of Amorphous-Carbon Thin-Films in the Presence of Magnetic Media Authors: Ramirez-AG Itoh-T Sinclair-R Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 3, pp 1508-1513 Abstract: Amorphous carbon thin films, which are often used as protective coatings for magnetic hard disks, were deposited in a carbon/cobalt alloy/carbon trilayers (20/10/20 nm) and subjected to thermal annealing and cooling. The associated microstructural changes were analyzed by in situ transmission electron microscopy (TEM). TEM micrographs show that the amorphous carbon in contact with the magnetic media increases in graphitic content at annealing temperatures near 400 degrees C. It fully crystallizes between 500 and 600 degrees C. The microstructural changes at these temperatures suggest that the metals of the magnetic layers mediate graphitization, similar to the behavior of other eutectic metal metalloid systems (e.g., Al-Si, Ag-Ge). Calorimetric and magnetic measurements are consistent with a graphitization mechanism that includes a diffusional process. This article presents the experiments and proposes a graphitization mechanism. (C) 1999 American Institute of Physics. [S0021-8979(99)06703-1]. Record 18 of 20. Title: Characterization of Interfacial Properties in Sputtered Co Cu Multilayers - X-Ray Reflectometry Compared with TEM and AFM Authors: Langer-J Krausslich-J Mattheis-R Senz-S Hesse-D Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 644-646 Abstract: Combining localised and global structural information we suggest that differences in the maenetoresistive effect in the first maximum of antiferromagnetic coupling in Co/Cu multilayers can be attributed to the number of magnetic shortcuts localised at grain boundaries. In particular evidence is given that the increased rms-roughness in samples without buffer as compared to samples grown on a Fe buffer can be attributed to a break off of the multilayer structure in adjacent grains. (C) 1999 Elsevier Science B.V. All rights reserved. Record 19 of 20. Title: Catalyst Supports Based on Encapsulated Magnetic Metal Particles Authors: Teunissen-W Geus-JW Full source: STUDIES IN SURFACE SCIENCE AND CATALYSIS 1999, Vol 121, pp 185-190 Abstract: Catalyst bodies considerably smaller than 1 mm are attractive for liquid phase reactions, but they cannot be readily separated from the liquid. Small magnetic particles, however, can be magnetically separated from the liquid, even when they are very small, e.g., 30 nm. The main drawbacks of the currently used ferromagnetic particles are their high chemical reactivity and clustering due to the hard magnetic nature. In this article, a procedure is described to produce small nickel-iron and cobalt-iron alloy particles. Exposure of these particles to methane or carbon monoxide, at 725 degrees C, leads to the encapsulation in graphitic carbon, which make them chemically inert. It is demonstrated that the final coercive force and remanence of the encapsulated iron-nickel and iron-cobalt particles are low and the saturation magnetization is elevated, as is required for successful application as a support for catalysts suspended in liquids. Record 20 of 20. Title: Elongation of Confined Ferrofluid Droplets Under Applied Fields Authors: Banerjee-S Fasnacht-M Garoff-S Widom-M Full source: PHYSICAL REVIEW E 1999, Vol 60, Iss 4, pp 4272-4279 Abstract: Ferrofluids are strongly paramagnetic liquids. We study the behavior of ferrofluid droplets confined between two parallel plates with a weak applied field parallel to the plates. The droplets elongate under the applied field to reduce their demagnetizing energy and reach an equilibrium shape where the magnetic forces balance against the surface tension. This elongation varies logarithmically with aspect ratio of droplet thickness to its original radius, in contrast to the behavior of unconfined droplets. Experimental studies of a ferrofluid-water-surfactant emulsion confirm this prediction. [S1063-651X(99)00210-X].