Grain boundary contribution to recoil loop openness of exchange-coupled nanocrystalline magnets

Abstract

It has been well known that recoil loop openness is related to soft-phase presence in exchange-coupled hard-soft nanocomposite magnets. Our study on recoil loop openness of exchange-coupled nanocrystalline magnets (both single-phase and composite) using a micromagnetic finite-element method has revealed that the recoil loop openness is also due to decreased grain size. Open recoil loops exist in single-phase magnets as well. Simulation of magnetization distribution in both nanocrystalline single-phase magnets and nanocomposite magnets shows that the openness of the recoil loops is correlated with unstable magnetization behavior in grain boundary and soft-phase regions, which is attributed to high energy state caused by exchange coupling in these regions. The simulation results are supported by experimental data.