Surface Roughness Reduction in $L 1_{0}$ Ordered FePd Alloy Thin Films Formed on MgO Single-Crystal Substrates with Different Orientations

L1₀ 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 L1₀ ordered structure grow epitaxially on MgO substrates when deposited at 600°C. Epitaxial films with disordered A1 structure prepared at 200°C transform into L1₀ ordered structure by annealing at 600 °C. Although L1₀ 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 L1₀ ordered alloy films with very flat surfaces, which are important for practical device applications.