Magnetic anisotropy of some heavy rare-earth metals

Abstract

Abstract The first order axial anisotropy coefficient, K2, has been evaluated for terbium at constant magnetic fields from torque measurements in its paramagnetic region. In this region K2 can also be calculated at constant magnetization from the known anisotropy in susceptibility between the basal plane and c axis. From the latter results, an extrapolation to 0 K has been made on the basis of the validity of the single-ion theory for the anisotropy of the heavy rare earths. This yields the following values in erg/cm3 for K2(0): Tb, 2.7 × 108; Dy, 3.1 × 108; Ho, 1.0 × 108; Er, −1.9 × 108. The basal-plane anistropy coefficient K66 of terbium has been determined at different temperatures and fields by direct torque measurements. It obeys the single-ion magnetization dependence with a value at 0 K of 2.9 × 106 erg/cm3.