Microstructure and magnetic properties of anisotropic polycrystalline Sm(Fe_0.8Co_0.2)₁₂ thin films with ThMn₁₂ structure

The ThMn₁₂-type hard magnetic compounds composed of rare earth elements and 3d ferromagnetic transition metals such as Fe have been known as possible candidates for the development of permanent magnet materials. In order to stabilize the ThMn₁₂ phase, the substitution of Fe with non-magnetic element M such as Ti, V, Mo and Si is required [1,2], which results in the reduction of saturation magnetization μ₀M_s. Kuno et al. reported that high μ₀M_s of 1.63 T in strip cast alloy by doping Zr in Sm site. and controlling the content of non-magnetic element M with the (Sm_0.8Zr_0.2) (Fe_0.75Co_0.25)Ti_0.5 composition [3]. Recently, Hirayama et al. showed excellent intrinsic hard magnetic properties with saturation magnetization μ₀M_s of 1.78 T, anisotropy field μ₀H_A of 12 T and Curie temperature T_c of 859 K for epitaxial Sm(Fe_0.8Co_0.2)₁₂ films prepared by sputtering process, which are superior to those of Nd₂Fe₁₄B [4], Owing to these promising intrinsic properties, the Sm(Fe_0.8Co_0.2)₁₂ compound can be a candidate for high performance permanent magnet applications. One drawback of ThMn₁₂ compound based magnets is their too low coericvity [5, 6]; however, considering the value of the anisotropy field, there is still room for improving coercivity. The purpose of the present investigation is to explore the possibilities for obtaining high coercivity in Sm(Fe_0.8Co_0.2)₁₂ based alloy using strongly textured polycys-talline thin films.