铁磁/反铁磁双层膜中冷却场对交换偏置场的影响

用铁磁畴壁模型研究了非补偿界面铁磁/反铁磁双层膜中冷却场（包括大小及其方向）对交换偏置场h_E的影响.结果表明：当冷却场的方向与反铁磁层磁易轴一致时，h_E大小与冷却场大小无关.当冷却场的方向偏离磁易轴时，h_E的大小随偏离角度的增大有缓慢的改变，但当冷却场的方向偏离到临界角度γ_c处，h_E的大小发生突变，其γ_c的大小随冷却场的增大而增大.特别是当冷却场的偏离角度大于γ_c后，h_E出现由负转正的现象，其转变点还与冷却场的大小有关.另外，h_E与铁磁层原子层数N_F的关系会发生由h_E∝N^-1_F向h_E∝N^-λ_F的转变，其中λ>1.其发生转变的条件与N_F、冷却场大小和方向密切相关. 关键词： 铁磁/反铁磁双层膜 交换偏置 冷却场

The influence of the cooling field on the exchange bias in ferromagnet/antiferromagnet bilayers system

The ferromagnetic domain wall model is used to investigate the influence of the cooling field （including its magnitude and orientation） on the exchange bias（h_E） in ferromagnet/antiferromagnet bilayers with uncompensated interface. The results show that h_E is independent of the magnitude of the cooling field when it is applied parallel to the easy axis of the antiferromagnet. When the cooling field deviates from the easy axis direction, h_E changes slowly with increasing field angle, but a sudden change is observed when the angle goes up to a critical angle γ_c, which γ_c increases with the cooling field increaseing. Especially, h_E has a transition from negative to positive when the field angle is beyond γ_c, and the transition point also relates to the magnitude of the cooling field. Moreover, the thickness dependence of the exchange bias exhibits a liner dependence on the inverse ferromagnet layer thickness, but yields a crossover from h_E∝N^-1_F to h_E∝N^-λ_F at a certain thickness （here λ>1）. This behavior is strongly dependent on the ferromagnet thickness, the magnitude and the angle of the cooling field.