The Change of the Curie Temperature of Iron-Nickel Alloys Due to Hydrostatic Pressure

Abstract

The change of the Curie temperature due to hydrostatic pressure was measured for two iron-nickel alloys with a nickel concentration of 30 and 32 atomic percent respectively. Hydrostatic pressure was produced with an apparatus of Bridgman’s type and the measurements of magnetization were performed by the ballistic method. The change of the Curie temperature due to pressure was estimated to be −3·10⁻³ and −2.7·10⁻³ deg. kg⁻² cm² for specimens with a nickel concentration of 30 and 32% respectively. Based on Smoluchowski’s fomula, the volume dependence of saturation magnetization at absolute zero 1⁄I₀·∂I₀⁄∂ω and that of the molecular field coefficient 1⁄N·∂N⁄∂ω for a 30% nickel alloy were found to be 27 and −16 from the experimental results. And then taking into consideration the volume dependence of the saturation magnetization at absolute zero, the relations among the volume dependence of the Curie temperature, molecular field coefficient and exchange integral are discussed.