Atomic ordering and magnetism in L1 0 ordered FePd alloys
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C compounds below a characteristic ordering temperature TO/D, frequently right up to the melting point, show a tendency to distribute the different sorts of atom preferentially on certain sublattices of the original atomic lattice of the disordered alloy. This state of longrange order (LRO) is a consequence of the atomic interaction energies, in this case, favoring unlike atoms as nearest neighbors. The new crystal structure can remain unchanged (for example, in Ni3Al, where the ordered L12 structure fully corresponds to the original fcc structure) or can be distorted as in L10-ordered TiAl, where the fcc structure changes into tetragonal. In particular, ferromagnetic L10-ordered alloys display a marked mechanical and magnetic anisotropy with the tetragonal c-axis of the distorted ordered domains being the ‘‘easy axis’’ of magnetization. Due to this high magnetic anisotropy, these alloys have a potential as magnetic and magneto-optical recording media, and a very high recording density may be achieved,
CHAISAK ISSRO, Doctor, formerly with the Institut fu¨r Materialphysik, University of Vienna, is with the Department of Physics, Faculty of Science, Burapha University, Chonburi 20131, Thailand. WOLFGANG ¨ SCHL, BOGDAN SEPIOL, and WOLFGANG PFEILER, Professors, PU are with the Institut fu¨r Materialphysik, University of Vienna, 1090 Vienna, Austria. Contact e-mail: [email protected] MADJID ABES, Doctor, GUY SCHMERBER, and VE´RONIQUE PIERRONBOHNES, Professor, are with IPCMS-GEMME, CNRS-ULP, 67034 Strasbourg Cedex 2, France. PETER F. ROGL, Professor, is with the Institut fu¨r Physikalische Chemie, University of Vienna, 1090 Vienna, Austria. WILLIAM A. SOFFA, Professor, is with the Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904. RAFAL KOZUBSKI, Professor, is with the M. Smoluchovski Institute of Physics, Jagellonian University, 30-059 Cracow, Poland. This article is based on a presentation made in the symposium entitled ‘‘Fourth International Alloy Conference,’’ which occurred in Kos, Greece, from June 26 to July 1, 2005, and was sponsored by Engineering Conferences International (ECI) and co-sponsored by Lawrence Livermore National Laboratory and Naval Research Laboratory, United Kingdom. METALLURGICAL AND MATERIALS TRANSACTIONS A
if these materials can be stabilized as low-dimensional magnetic structures.[1,2] It is known that atom jump processes can be considerably changed in low-dimensional structures such as thin films due to increased crystal defect density and by processes of surface diffusion or interdiffusion with substrate, buffer, or capping layers that may start at comparatively low temperatures. Having investigated ordering kinetics in massive samples, we recently began to apply our successful techniques to intermetallic thin films. Within the interesting group of L10-ordered ferromagnetic alloys, FePd, FePt, CoPt, with their mechanically and magnetically anisotropic ordered phases, we used FePd as a model system. It shows a lower order-disorder tr
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