Effect of Pressure on the Curie Temperature of Rare-Earth Metals. I. Gadolinium

Abstract

An experimental investigation has been undertaken for the purpose of learning the effect of interatomic distance on the magnetic exchange interaction in ferromagnetic rare-earth metals. The first material which has been studied is gadolinium. The equipment used was the high-pressure apparatus of Professor G. C. Kennedy of the Institute of Geophysics (UCLA). A toroidal-shaped specimen of gadolinium was subjected to pressures up to about 40 kilobars (kbar). The gadolinium toroid served as a transformer core. A constant input voltage was applied and the output voltage was studied as a function of pressure and temperature. The Curie temperature, obtained from the output voltage, was found to be depressed linearly with pressure at a rate of -1.60\ifmmode^\circ\else\textdegree\fi{}C/(kbar) up to 21.5 kbar. Between 21.5 and 26.7 kbar a phase transition to a nonferromagnetic state occurred.