L10 Ordered FePd, FePt, and CoPt Thin Films With Flat Surfaces Prepared on MgO(110) Single-Crystal Substrates

FePd, FePt, and CoPt alloy thin films are prepared on MgO(110) single-crystal substrates by using two different methods. One is one-step method consisting of deposition at an elevated substrate temperature of 600 degrees C and the other is two-step method consisting of low-temperature deposition at 200 degrees C followed by annealing at 600 degrees C. The crystal structure, the crystallographic orientation, and the surface morphology are compared. L1(0) ordered FePd, FePt, and CoPt films epitaxially grow on the substrates with three variants, (110), (101), and (011), when deposited at 600 degrees C. The c-axis of L1(0)(110) variant is lying in the film plane, whereas those of L1(0)(101) and L1(0)(011) variants are 45 canted from the substrate surface. Disordered FePd, FePt, and CoPt single-crystal films of (110) orientation are formed by deposition at 200 degrees C. An A1-L1(0) phase transformation occurs along A1[001], A1[010], and A1[001] by annealing the disordered films at 600 degrees C. The annealed films thus consist of three L1(0) variants. Similar final crystal structure and orientation are realized in the FePd, the FePt, and the CoPt films prepared by employing the two different methods. The L1(0) ordered films prepared by one-step method have island-like surfaces involving facets, whereas those prepared by two-step method have very flat surfaces with the arithmetical mean roughness lower than 0.3 nm. The two-step method is useful for preparation of L1(0) ordered films with flat surfaces.