Magnetic anisotropy in RCo3 (R = Lu and Y) single crystals

We report on magnetization measurements of LuCo₃ and YCo₃ single crystals. These compounds show an instability of the 3d-subsystem, whereby the Co atoms go from a low-spin to a high-spin state in applied magnetic field. In the low-spin state, we find a pronounced anisotropy of the saturation magnetization for LuCo₃ and YCo₃, which can potentially lead to a large error in the determination of the anisotropy constant, K₂, whereas the constant, K₁, is much less affected. We also show that Belov-Arrott plots yield different values of the Curie temperature than obtained by magnetization curves along different crystallographic directions.