Y₁₇Co₈₃ and Gd₁₇Co₈₃ (at. %) alloy thin films are prepared on Cu(111) underlayers epitaxially grown on MgO(111) substrates at a substrate temperature of 500 °C by molecular beam epitaxy. The growth behavior and the film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. YCo₅ and GdCo₅ ordered alloy crystals epitaxially grow on the Cu underlayers. The epitaxial films consist of two (0001) variants whose orientations are rotated around the film normal by 30° each other. The epitaxial orientation relationships are (YCo₅ or GdCo₅)(0001)[1100] || Cu(111)[112] (type A) and (YCo₅ or GdCo₅)(0001)[1120] || Cu(111)[112] (type B). The volume ratios of two variants, V_{type A}:V_typeB, in YCo₅ and GdCo₅ films are estimated to be 65:35 and 72:28, respectively. The long-range order degrees of YCo₅ and GdCo₅ films are respectively determined to be 0.63 and 0.65. These ordered alloy films show perpendicular magnetic anisotropies reflecting the magnetocrystalline anisotropies of YCo₅ and GdCo₅ crystals.

  Fe_100-xNi_x (x = 0-100 at. %) alloy epitaxial films of 10 nm thickness are prepared on Cr(211) underlayers at room temperature by using a radio-frequency magnetron sputtering system. The film growth behavior and the crystallographic properties are investigated by in-situ reflection high-energy electron diffraction and pole-figure X-ray diffraction. bcc(211) crystal epitaxially nucleates on the underlayer for the Fe_100-xNi_x films with x = 0-70 at. %. The bcc structure is stabilized up to 10 nm thickness for the compositional range of x = 0-50 at. %, whereas the Fe₄₀Ni₆₀ and the Fe₃₀Ni₇₀ crystals with bcc structure (x = 60-70 at. %) start to transform into fcc structure with increasing the thickness beyond 2 and 5 nm, respectively. The bcc-fcc phase transformation occurs through atomic displacements parallel to bcc(110) and bcc(101) close-packed planes which are 60° canted from the perpendicular direction. The crystallographic orientation relationship is similar to the Kurdjumov-Sachs relationship. When the x value is increased beyond 80 at. %, metastable hcp(1100) crystal coexists with bcc(211) crystal. The volume ratio of hcp to bcc crystal increases as the x value increases from 80 to 100 at. %. With increasing the thickness, the hcp crystal also starts to transform into fcc structure through atomic displacement parallel to hcp(0001) close-packed plane, which is similar to the case of bulk phase transformation in the Shoji-Nishiyama relationship.