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The FePt, FePd, CoPt, and CoPd epitaxial thin films are prepared on MgO(001) single-crystal substrates by ultrahigh vacuum RF magnetron sputtering. The effects of the magnetic material and the substrate temperature on the film growth, the film structure, and the magnetic properties are investigated. The L10 ordered phase formation is observed for FePt, FePd, and CoPt films prepared at temperatures higher than 200, 400, and 600 °C, respectively, whereas that is not recognized for CoPd films. The L10-FePd(001) single-crystal films with the c-axis normal to the substrate surface are formed, whereas the FePt and CoPt epitaxial films include L10(100) crystals whose c-axis is parallel to the substrate surface, in addition to the L10(001) crystals. Upon increasing the substrate temperature, the ordering degree increases. A higher ordering parameter is observed in the order of FePd > FePt > CoPt. The magnetic properties are influenced by the crystal structure, the crystallographic orientation of the L10 crystal, and the ordering degree.

ordered FePd alloy epitaxial thin films are prepared on MgO substrates of (001), (110), and (111) orientations by two different methods; by direct deposition at high temperature of 600 C and by preparation of film at a low temperature of 200 C followed by high temperature annealing at 600 C. The influence of preparation method on film structure, order degree, surface roughness, and magnetic property are investigated. Films with ordered structure grow epitaxially on MgO substrates when deposited at 600 C. Epitaxial films with disordered structure prepared at 200 C transform into ordered structure by annealing at 600 C. Although order degree is similar between two kinds of FePd film prepared by different methods, the surface roughness and coercivity are different. The films prepared by annealing have very flat continuous surfaces as well as lower coercivities which results from easy movement of domain walls. The two step process employing low temperature film deposition followed by high temperature annealing is very effective in the preparation of ordered alloy films with very flat surfaces, which are important for practical device applications.Index Terms-Annealing, FePd alloy thin film, phase transformation from to , surface roughness.

Abstract. FePd, FePt, and CoPt alloy thin films are prepared on MgO(001) single-crystal substrates by employing a two-step method consisting of sputter deposition at low-temperature (room temperature) followed by high-temperature annealing at 600 °C. FePd, FePt, and CoPt single-crystal films with disordered structure (A1) grow epitaxially on MgO substrates at room temperature. By annealing these disordered films at 600 °C, a transformation from A1 to L1 0 -ordered phase occurs. The order degrees of annealed FePd, FePt, and CoPt films are 0.63, 0.38, and 0.16, respectively. The films before annealing have very flat surfaces and the flat surfaces are kept after annealing. The arithmetical mean surface roughness values of annealed FePd, FePt, and CoPt films are 0.3, 0.1, and 0.2 nm, respectively. The two-step method is considered to be useful for preparation of FePd, FePt, and CoPt alloy thin films with flat surfaces, which are necessary for practical applications.

FePd-alloy thin films of 40 nm thickness are prepared on MgO single-crystal substrates of (001), (110), and (111) orientations by employing a two-step method consisting of deposition at a low temperature of 200 °C followed by annealing at a higher temperature in a range from 300 to 600 °C. The influences of substrate orientation and annealing temperature on the ordered phase formation and the surface roughness are investigated. FePd films with disordered A1 structure grow epitaxially on MgO substrates of all the orientations at 200 °C. Transformation from A1 to L10 phase starts to be observed in FePd films formed on the respective MgO substrates after annealing at 300, 500, and 600 °C. With increasing the annealing temperature up to 600 °C, the order degrees of FePd films formed on MgO substrates of (001), (110), and (111) orientations respectively increase to 0.63, 0.29, and 0.33. The films before annealing have very flat surfaces and the flat surfaces are kept after annealing for all the substrate orientations and the investigated annealing temperatures. The arithmetical mean surface roughness values of FePd films formed on MgO(001), (110), and (111) substrates after annealing at 600 °C are 0.2, 0.2, and 0.3 nm, respectively. The L10-FePd film formed on MgO(001) substrate shows a perpendicular magnetic anisotropy, whereas the L10-FePd films formed on MgO(110) and (111) substrates have in-plane anisotropies. The magnetic anisotropy is influenced by the c-axis distribution and the order degree.