外应力对铁磁/反铁磁体系交换偏置的影响及阶跃现象

Using the principle of minimal energy and S-W model, the effect of the applied stress on exchange bias in ferromagnetic (FM) / antiferromagnetic (AFM) bilayers has been investigated. When the applied field is absent, according to the relation between the energy of the system and the orientation of ferromagnetic magnetization, it is found that the system will be in monostable state or bistable state, which is controlled by the competition between the uniaxial anisotropy and the exchange anisotropy. Monostable state or bistable state of the system determine the angular dependence of exchange bias immediately. When the applied field is parallel to the intrinsic easy axes and intrinsic hard axes, by analyzing the magnetization process, we found that one of the switching field of the hysteresis loop shows a jump, while the other is kept constant, and consequently the exchange bias field and the coercivity will appear a step. The numerical calculations indicate that the exchange bias field and the coercivity have a greater value at the point of step. Both the magnitude and the orientation of the applied stress will significantly affect the exchange bias by making a transition between monostable state and bistable state in the system. This transition induces a significant change in angular dependence of the exchange bias. Our results demonstrate that the applied stress is a viable way to control and tune the exchange bias of the FM/AFM bilayers.