Comparison of temperature driven ordering in bulk foil and thin film of L1 0 ordered FePd
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Comparison of temperature driven ordering in bulk foil and thin film of L10 ordered FePd Chaisak Issro1, Wolfgang Püschl1, Wolfgang Pfeiler1, Bogdan Sepiol1, Peter F. Rogl2, William A. Soffa3, Manuel Acosta4 and Véronique Pierron-Bohnes4 1
Institut für Materialphysik, University of Vienna, Strudlhofgasse 4, A-1090 Vienna, Austria Institut für Physikalische Chemie, University of Vienna, Währingerstraße 42, A-1090 Vienna, Austria 3 Dept. of Material Science and Engineering, University of Pittsburgh, 842 Benedum Hall, Pittsburgh, PA 15261, U.S.A. 4 IPCMS-GEMME, CNRS-ULP, 23 rue du Loess, BP 43, F-67034 Strasbourg Cedex 2, France 2
ABSTRACT Changes in the degree of long-range order of 10 µm thick FePd foil are presented and compared with results on 50 nm thick FePd films. The films were produced by dc and rf magnetron co-sputtering on Si as well as by molecular beam epitaxy co-deposition on MgO substrates. Long-range order was studied by electrical resistivity measurement, X-ray diffraction and Mößbauer spectroscopy.
INTRODUCTION It is well known that L10 long-range ordered intermetallic compounds show advantageous technological properties such as high corrosion resistance and promising high-temperature mechanical strength. Due to their tetragonal distortion in the ordered state these intermetallics display a very marked mechanical and magnetic anisotropy with the tetragonal c-axis being the easy axis of magnetization. This gives hope for their technical application in high-density magnetic and magneto-optic recording when the c-axis of the ordered domains is oriented perpendicular to the surface, especially if these materials can be stabilised in the form of lowdimensional magnetic structures. Thermodynamic stability is essential for the technical application and performance of these materials. Therefore, we have already studied in massive FePd the change of long-range order (LRO) during isochronal and isothermal heat treatment starting from the disordered state [1]. Now we use our methods to study the changes in the degree of order in thin films of FePd [2]. In the present paper we present first results on FePd films sputtered on Si and co-deposited on MgO by molecular beam epitaxy (MBE) and compare them with a thin foil of FePd (≈10µm). We studied the as-prepared state and the changes during the subsequent heat treatments.
EXPERIMENTAL FePd polycrystalline foil containing 49.8±0.5 at% Fe was cold-rolled at room temperature (RT) to a thickness slightly below 10µm. FePd thin film containing 50±5 at% Fe was non-epitaxially deposited by dc and rf magnetron co-sputtering on Si(100) substrate at room temperature. The base pressure of the
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sputtering chamber was approximately 9x10-9 Torr, and Ar gas used for co-deposition had a pressure of nearly 5x10-3 Torr. A Pd target was used with a dc current of 144 mA and a sputtering rate of 1.25 Å/s. The rf power for the Fe target was 203 W at 1.00 Å/s sputtering rate. Epitaxial FePd thin films (composition 50±2 at% Fe) were deposited on MgO(001) substrate by
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