Numerical study of the exchange-bias effect in nanoparticles with ferromagnetic core/ferrimagnetic disordered shell morphology

We have used the Monte Carlo simulation technique to investigate the effect of a ferrimagnetic disordered shell on the hysteresis behavior of composite magnetic nanoparticles with ferromagnetic core/ferrimagnetic disordered shell morphology. We have examined the cooling field (Hcool) dependence of the exchange bias (Hₑₓ), the coercive field (Hc), and the remanent magnetization (Mᵣ) and we find that an increase in Hcool results initially in an increase in Hₑₓ, Hc, and Mᵣ, while further increase in Hcool causes a reduction in Hₑₓ and Hc, but Mᵣ remains constant. Our simulations show that an increase in the shell thickness for a given core size enhances the exchange bias field and reduces the remanent magnetization, the vertical shift, and the training effect. We also find that a reduction in the core size for a given particle size results in an increase in both exchange bias and coercive field. This behavior is reversed as the temperature increases. Our results are in good agreement with experimental findings.