Microstructure and magnetic properties of anisotropic polycrystalline Sm(Fe0.8Co0.2)12 thin films with ThMn12 structure

Abstract

The ThMn $_{12} -$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 ThMn 12 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 $\mu _{0}M_{S}$. Kuno et al. reported that high $\mu _{0}M_{S}$ 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 0.8 Zr 0.2 ) (Fe 0.75 Co 0.25 ) Ti 0.5 composition [3]. Recently, Hirayama $et al$. showed excellent intrinsic hard magnetic properties with saturation magnetization $\mu _{0}M_{S}$ of 1.78 T, anisotropy field $\mu _{0}H_{A}$ of 12 T and Curie temperature $T_{C}$ of 859 K for epitaxial Sm(Fe 0.8 Co 0.2 ) 12 films prepared by sputtering process, which are superior to those of Nd 2 Fe 14 B [4]. Owing to these promising intrinsic properties, the Sm(Fe 0.8 Co 0.2 ) 12 compound can be a candidate for high performance permanent magnet applications. One drawback of ThMn 12 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 0.8 Co 0.2 ) 12 based alloy using strongly textured polycrystalline thin films.