X-ray Magnetic Linear Dichroism of Fe-Ni Alloys on Cu(111)
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X-ray Magnetic Linear Dichroism of Fe-Ni Alloys on Cu(111) T.F. Johnson,1 S. Chiang,1 Y. Sato,1 D.A. Arena,2 S.A. Morton,3 M. Hochstrasser,2 J.G. Tobin,2 J.D. Shine,1 J.A. Giacomo,1 G.E. Thayer,1 D.P. Land,4 X.D. Zhu1 1 Dept. of Physics, University of California, Davis 2 Lawrence Livermore National Laboratory, Livermore 3 University of Missouri, Rolla 4 Dept. of Chemistry, University of California, Davis ABSTRACT We have prepared FexNi1-x multilayers on Cu(111) in order to learn how to control the structure and magnetism of these thin alloy films, which are relevant to the giant magnetoresistance (GMR) effect used in magnetic disk drive heads. Using the Spectromicroscopy Facility (7.0.1.2) on Undulator Beamline 7.0 at the Advanced Light Source, we have measured X-ray magnetic linear dichroism (XMLD) signals from both Fe and Ni 3p lines for fourteen different thin Ni-Fe alloy films on Cu(111), with Fe concentration ranging from 9% to 84% and for a variety of film thicknesses. The Curie temperature for all of these samples was in the range 200K to 500K. For many of these films, the Curie temperature was considerably lower than was previously seen for similar films deposited on Cu(100). For a particular Fe concentration x, the Curie temperature increases with alloy film thickness. For a specific film thickness, the Curie temperature has a maximum near x≈0.4. INTRODUCTION The ability to control growth at the atomic level has led to renewed interest in the study of magnetism and magnetic materials. This control allows for the study of the relationship between magnetic and structural properties for optimization of magnetic devices based on thin film technologies, as well as testing the theoretical predictions for such systems.1 We are studying layer-by-layer synthesis of ultrathin metal films by controlling the composition and structure of these films at the monolayer level, including the interfacial region. We have prepared FexNi1-x multilayers using simultaneous evaporation of pure Ni and Fe on Cu(111) in order to better understand the GMR effect in NiFe/Cu systems that are relevant to magnetic disk drive heads. Using core-level photoelectron spectroscopies on magnetized samples allows for exploitation of the fact that symmetry is broken due to the presence of magnetization. The effect is due to spin-orbit interaction in the presence of exchange interaction. X-ray magnetic linear dichroism (XMLD) is one such technique that clearly exhibits asymmetry due to magnetization. XMLD can be observed in angle resolved, spin-integrated photoemission experiments for ppolarized light under oblique incidence.2 The first example of this effect was shown on a thin Fe(001) film, for which the Fe 3p core level peak position and line shape changed when the magnetization of the sample was reversed.2 Because of its dependence on photoemission from a core level, the effect can be used for surface sensitive, element-specific magnetometry. In this study, we have observed this effect for 14 samples of different thicknesses with Fe concentratio
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