Pressure Dependence of the Magnetization of Invar and Silectron from 30–450 kbar

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Abstract
Measurements of the change in saturation magnetization of Invar and Silectron subjected to shock-wave compression from 30 to 450 kbar show that Invar exhibits a constant coefficient of saturation magnetization change with pressure, Ms−1(dMs/dp) and that Silectron experiences a pressure-induced transition to a nonferromagnetic phase. Shock waves are generated in tape-wound core samples by projectile impact techniques which allow experiments in small pressure increments over a wide range in pressure. The Invar measurements give a value for Ms−1(dMs/dp) of −1.3×10−2 kbar−1 up to a magnetization change of 90% of the saturation magnetization. This value is the same as that obtained in previous static measurements to 5 kbar. Measurements on Silectron (grain-oriented 3% Si-97% Fe) cores show a change in magnetization beginning at 150 kbar which is the pressure at which a first-order transition has been detected from previous shock-wave pressure-volume measurements. The present measurements indicate that the high-pressure phase of Silectron is nonferromagnetic and show that a mixed-phase region extends to a pressure of 225 kbar. These shock-wave measurements cover a pressure range which is about two orders of magnitude greater than that used previously in static magnetization vs pressure measurements.