Micromagnetic study of magnetization reversal in inhomogeneous permanent magnets

Abstract

Macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets. Complex materials such as hard-soft exchange-coupled magnets or just real technical materials with impurities and inhomogeneities exhibit complex magnetization behavior. Here we investigate the effects of size, volume fraction, and surroundings of inhomogeneities on the magnetic properties of an inhomogeneous magnetic material via micromagnetic simulations. The underlying magnetization reversal and coercivity mechanisms are revealed. Three different demagnetization characteristics corresponding to the exchange coupling phase, semi-coupled phase, and decoupled phase are found, depending on the size of inhomogeneities. In addition, the increase in the size of inhomogeneities leads to a transition of the coercivity mechanism from nucleation to pinning. This work could be useful for optimizing the magnetic properties of both exchange-coupled nanomagnets and inhomogeneous single-phase magnets.