Effect of Hydrostatic Pressure on Magnetic Properties of Tb and Dy

Abstract

Measurements of weak-field ac susceptibilities have been made on Tb and Dy under hydrostatic pressures up to about 6 kbar, to investigate the pressure effects on the magnetic transition temperatures, and on the effective number of Bohr magnetons neff in the paramagnetic state. In addition, the compressibility necessary for the correction was measured. In the paramagnetic temperature range, the measured susceptibilities followed the Curie—Weiss law well, and neff decreased with pressure; (1/neff) (dneff/dp) is −9.6×10−7 bar−1 for Tb and −6.1×10−7 bar−1 for Dy. These negative values simply suggest the transition of electrons from the 4f shell to the conduction band with decreasing atomic distance. An anomaly in the compressibility was observed at the magnetic transition temperatures in agreement with the thermodynamical Ehrenfest relation for a second-order transition.