The Effect of the Sweeped Magnetic Field and Interface Magnetic Dilution on the Exchange Bias and Coercivity for FM/AFM Films

The roles of the sweeped magnetic field and the interface magnetic dilution on the exchange bias H-e and coercivity H-c for ferromagnetic/ antiferromagnetic (FM/AFM) films have been studied by Monte Carlo method. The simulated results indicate that: (1) For the small Monte Carlo steps (MCSs), the values of H-e and the blocking tempreture T-b reduce evidently with increasing MCSs; For the larger MCSs, the values of H-e and T-b decrease gently with increasing MCSs. (2) The values of H-e and T-b decrease evidently with increasing values of H-0 (HN0). At low temperature and little HN0, the asymmetric loop may appear, which is attributed to the competition between the relaxation time and the period of the external magnetic field. (3) The magnetic dilution ratio x1 in the interface layer has an important influence on the exchange bias and coercivity. There exist two maxima at x1=0.3 and 0.5 in H-e-T curve, while the exchange bias becomes small and even disappears for x1=0.0, 0.1, 0.9, 1.0. Moreover, based on the percolation model, small AFM domains (clusters) divided by FM atoms in the interface layer may be responsible for the observed maxima at x1=0.3-0.5 in H-e-T curves.