Magnetization and magnetic anisotropy of R2Co14B and Nd2(Fe1-x Cox) 14B measured on single crystals

Abstract

Magnetization and anisotropy field of R2Co14B with R being La, Nd, and Gd and of Nd2(Fe 1-xCox)14B have been measured on single-crystal specimens. The cobalt sublattice has a planar anisotropy: K 1=-1.30 MJ/m3 at 4.2 K for La2Co 14B with the [110] direction being the room-temperature easy direction of magnetization. The rare-earth ions in R2Co 14B experience a smaller exchange field than in R 2Fe14B, which results in a rapid reduction of the rare-earth sublattice magnetization and anisotropy with increasing temperature. Because of the planar anisotropy of cobalt and the weaker R-Co interactions than R-Fe, the anisotropy field of Nd2(Fe 1-xCox)14B turns out to be almost independent of the cobalt concentration in a temperature range between 300 and 500 K.