Recent developments in rare-earth nitrides and carbides

Abstract

In this article, we review our recent studies on new rare-earth intermetallic compounds including the Ga, Si substituted 2:17-type compounds, their nitrides and carbides, and the Sm 3(Fe,Ti) 29N 5 compounds. Much of our recent work has been focused predominantly in the Sm 2(Fe,Ga) 17C x alloys, where we used melt-spinning and subsequent annealing to obtain a high coercivity. The highest coercivity obtained so far was in Sm 2Fe 14Ga 3C 2.5, with a value of 12.8 kOe at room temperature. The off-stoichiometric Sm 2Fe 14− x Co x Si 2N y nitrides maintain the Th 2Zn 17-type structure but with a unit-cell expansion ΔV V up to 5% compared to the host materials. The Sm 2Fe 14− x Co x Si 2C z carbides maintain the Th 2Zn 17-type structure when z = 1 and transform to BaCd 11-type structure when z = 2. A very large anisotropy field with H a value of 227 kOe for Sm 2Fe 14Si 2N 2.6 and 276 kOe for Sm 2Fe 10Co 4Si 2N 2.3 is observed at low temperature (1.5 K). The Sm 3(Fe,Ti) 29N 5 compound and its nitrides show very interesting magnetic properties. Both of these compounds exhibit ferromagnetic ordering with T c of 486 and 750 K, respectively. The room-temperature saturation magnetization is 119 e.m.u. g −1 for the parent compounds and 145 e.m.u. g −1 for the nitrides. The easy-magnetization direction changes from planar to uniaxial upon nitrogenation. The anisotropy field for the nitrides is 12 T at room temperature and 25 T at 4.2 K.