FePd, FePt, and CoPt alloy epitaxial thin films with flat surface grown on MgO(111) substrate

FePd, FePt, and CoPt alloy epitaxial films of 40 nm thickness are prepared on MgO(111) single-crystal substrates by employing two different methods. One is a one-step method consisting of high-temperature deposition at 600 degrees C and the other is a two-step method consisting of low-temperature deposition at 200 degrees C followed by annealing at 600 degrees C. Although the preparation method is different, similar final crystal structures are realized for all the film materials. FePd and FePt alloy films grow on the substrates with six L1(0)(111) variants, whose c-axes are about 35 degrees canted from the substrate surface and rotated around the film normal by 60 degrees each other. The order degrees of FePd and FePt films prepared by one- and two-step methods, (Sone-step, Stwo-step), are estimated to be (0.25, 0.33) and (0.08, 0.15), respectively. On the contrary, L1(0) ordered phase formation is not recognized for CoPt alloy films. The films prepared by one-step method have rough surfaces surrounded by side facets, whereas the films prepared by two-step method have very flat surfaces with the arithmetical mean roughness of 0.3 nm. The two-step method is useful for preparation of L1(0) ordered films with flat surface.