Ultrasound induced irreversible changes in the magnetization of highly magnetostrictive materials Tb0.27Dy0.73Fe2 and MnBi

Abstract

A sample, after being saturated in a high magnetic field, is in an unstable remanent state in a low or reversed magnetic field. Application of a burst of ultrasound at this point will result in an irreversible decrease in the remanent magnetization. By subsequently changing the magnetic field, and applying a second burst of ultrasound, a reduced irreversible decrease is effected. This observed behavior is a measure of the statistical correlation between the two magnetic states of the sample. We have successfully described this behavior with a modified Preisach model. We have observed irreversible changes in the magnetization of Tb0.27Dy0.73Fe2 (λ111 = 1.6×10−3) as large as 50% of the remanent magnetization, or 0.4% of the saturation magnetization, induced by ultrasound bursts of 107 dyne/cm2 at 20 °C. In MnBi (λs = −8×10−4) crystals in Bi, irreversible effects as large as 1.8% of the remanent magnetization, or 0.6% of the saturation magnetization, have been observed at 120 K.