Effects of magnetostriction on domain wall dynamics inside multi-grains soft magnet revealed by micromagnetic simulations

Abstract

Magnetostriction plays a key role in magnetization dynamics inside soft magnetic materials, which are widely used in electronic devices for inductor cores. In general, the performance of the soft magnetic device is governed by magnetization dynamics such as domain-wall motions. Thus, it is indispensable to understand how magnetostriction affects the magnetization dynamics. We performed micromagnetic simulations in order to clarify the effects of the magnetostriction. To simulate the magnetostriction, we have to solve the elastic equations of the crystal structure.[1,2] The magnetization generates strains of the crystal structure, and deformations of the crystal are affected by the distant magnetization. We solved equations of motions for the strains, and we obtained the magnetostrictive field. We parallelized simulations using Message Passing Interface.[3] Figure 1 shows a simulation model containing two grains. Inside the grains, we consider strip-shape magnetic domains. The crystal axes are rotated -20 and 20 degrees from the x-direction in the grain A and B, respectively. We applied AC magnetic field along the x-direction. The frequency of the AC magnetic field is 100MHz. We also applied static external stress parallel to the crystal axis of the grain A. The magnetic material is Fe. Figure 2 shows energy losses as a function of the external stress using the simulation results. When the tensile strain is 20 MPa, the energy loss is 1.8 times larger than that without stress. The results of this work show that the energy loss strongly depends on the stress and the microstructure of the soft magnetic materials.