Effect of Iron Substitution on the High-temperature Properties of Sm(Co,Cu,Ti)_z Permanent Magnets

Abstract

Recently, Ti-substituted Sm-Co permanent magnets have attracted renewed attention due to their interesting high-temperature coercivity. Our presentation deals with the effect of iron substitutions on the magnetic properties of the materials. X-ray diffraction shows that the investigated Sm(Co,Fe,Cu,Ti)z materials (z = 7.0 -7.6) are two-phase magnets, consisting of 1:5 and 2:17 regions. The iron content affects both the coercivity and the magnetization. Depending on composition and heat treatment, some samples show a positive temperature coefficient of the coercivity in the temperature range from 22 9C to 550 9C. Moderate amounts of iron enhance the room-temperature coercivity. For example, the room-temperature coercivity of Sm(Co 6 .oFeo. 4 Cuo.6Ti0. 3 ) is 9.6 kOe, as compared to 7.6 kOe for Sm(Co6.aCuo.6Tio. 3 ). At high temperatures, the addition of Fe has a deteriorating effect on the coercivity, which is as high as 10.0 kOe at 500 '-C for Sm(Co6. 4 Cu0.6Tio. 3 ). The room-temperature magnetization increases on iron substitution, from 73 emu/g for Sm(Co6. 4 Cuo.6Tio. 3 ) to 78 emu/g for Sm(Co 6 .oFeo. 4 Cuo.sTi0. 3 ). The observed temperature dependence is ascribed to the preferential dumbbell-site occupancy of the Fe atoms.