Intrinsic magnetic properties of (Sm,Gd)Fe12-based compounds with minimized addition of Ti

Abstract

SmFe12-based compounds with the ThMn12 type structure are considered to be potential candidates for rare-earth-lean permanent magnets; however, their poor phase stability has hindered practical application. In this work, the effects of Gd on the phase stability of the ThMn12 structure and the elimination of α-Fe for (Sm0.8Gd0.2)(Fe0.8Co0.2)12-xTix (x = 0.5, 0.6, 0.65, 0.75, 0.85, and 1) compounds are investigated. A single 1:12 phase was obtained for (Sm0.8Gd0.2)(Fe0.8Co0.2)11.25Ti0.75 compound with excellent intrinsic magnetic properties at 300 K with saturation magnetization, μ0Ms = 1.46 T, anisotropy field, μ0Ha = 9.24 T, and Curie temperature, Tc = 816 K. Unlike the Gd-free sample, the rapid decay of μ0Ms and μ0Ha at elevated temperatures was hindered for the Gd-doped sample; this originated from the hybridization between 5d orbitals of Gd and 3d orbitals of Fe along with the increase in magnetic coupling between the rare earth (RE) and Fe sublattices. (Sm0.8Gd0.2)(Fe0.8Co0.2)11.25Ti0.75 has a higher magnetic anisotropy field above 400 K compared with those of the previously reported SmFe12-based compounds Sm(Fe0.8Co0.2)11Ti1 and (Sm0.8Zr0.2)(Fe0.8Co0.2)11.5Ti0.5 and Nd2Fe14B compound.