Effects of magnetic frequency and the coupled magnetic-mechanical loading on a ferromagnetic shape memory alloy

Abstract

Abstract In the present work, the microstructure evolution and macro-response of a ferromagnetic shape memory alloy under stimuli of magnetic fields with different frequency and coupled magnetic-mechanical loading are investigated via a real-space phase field simulation. It is found that the coercive field is reduced from 0.724 to 0.423 with the magnetic frequency f decrease from 2.5 × 10 − 5 Hz to 0.833 × 10 − 5 Hz, wherein the concomitant domain wall motion and magnetization rotation are captured as well. Moreover, simulation results demonstrate that, under the coupled magnetic-mechanical loading, the coercive field of the magnetic hysteresis loop could be reduced by applying a compressive strain perpendicular to the magnetic field direction. The domain evolution is mainly divided into three types during the coupled magnetic-mechanical loading, namely (a) domain wall motion with the magnetization rotation, (b) pure magnetization rotation, and (c) 180° domain coordinated domain switching. To better understand the domain evolution, we propose an index S = m 1 avg + m 2 avg , with m 1 avg and m 2 avg indicating the absolute value of the averaged magnetization component m 1 and m 2 over the whole studied system, to characterize the magnetization change during the microstructure evolution.