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−xCo_x)₁₄B have been measured on single‐crystal specimens. The cobalt sublattice has a planar anisotropy: K₁=−1.30 MJ/m³ at 4.2 K for La₂Co₁₄B with the [110] direction being the room‐temperature easy direction of magnetization. The rare‐earth ions in R₂Co₁₄B experience a smaller exchange field than in R₂Fe₁₄B, 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−xCo_x)₁₄B turns out to be almost independent of the cobalt concentration in a temperature range between 300 and 500 K.