Magnetization of single-crystal terbium at very low temperatures by nuclear orientation

Abstract

We report an investigation of the magnetization of high-purity single crystal terbium below 50 mK, using the nuclear orientation of¹⁶⁰Tb, which substitutionally replaces naturally-occurring, monoisotopic¹⁵⁹Tb. The nuclear alignment is determined as a function of applied magnetic field, and can be related to the macroscopic magnetization of the host crystal by a suitable model. In the easy direction (b-axis), a very rapid rise is seen in the first 7 mT of applied field; this is followed by a pleateau region up to 0.1 T, then a slow saturation, completed at ca. 0.4 T. Along an a-axis, a similar rapid increase to about 50% of saturation is observed below 10 mT, followed by a slow, nearly linear increase which agrees with that calculated for domain rotation using the measured crystalline anisotropy constants.