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Micromagnetic Simulation of Amorphous Ferrimagnetic TbFeCo Films with Exchange Coupled Nanophases

Amorphous ferrimagnetic TbFeCo thin films are found to exhibit exchange bias effect near the compensation temperature by magnetic hysteresis loop measurement. The observed exchange anisotropy is believed to originate from the exchange interaction between the two nanoscale amorphous phases distributed within the films. Here, we present a computational model of phase-separated TbFeCo using micromagnetic simulation. Two types of cells with different Tb concentration are distributed within the simulated space to obtain a heterogeneous structure consisting of two nanoscale amorphous phases. Each cell contains separated Tb and FeCo components, forming two antiferromagnetically coupled sublattices. Using this model, we are able to show the existence of exchange bias effect, and the shift in hysteresis loops is in agreement with experiment. The micromagnetic model developed herein for a heterogeneous magnetic material may also account for some recent measurements of exchange bias effect in crystalline films.