Exchange bias training effect under different energy dissipation pattern

Abstract

The phenomenon of exchange bias training effect is successfully obtained by introducing an out-of-step of energy dissipation of ferromagnet and antiferromagnet. The numerical results suggest that the energy dissipation pattern of the antiferromagnet plays a crucial role for the understanding of the exchange bias training effects, e.g., when the energy dissipation pattern of the antiferromagnet follows power-law function, the best fit function for the dependence of exchange bias on the cycle number is power-law. The physical mechanism that the amount of the coercive field shift in the descent branch is larger than that of ascent branch for the hysteresis loop measurement and the coercivity of ferromagnet/antiferromagnet bilayers is always larger than that of the corresponding ferromagnet layer has been illuminated, respectively. Moreover, under the different values of damping parameter, the anomalous training effect observed by recent experiment [Z. Shi et al., Appl. Phys. Lett. 93, 222504 (2008)] and the conventional training effect can also be elucidated, respectively.