反铁磁耦合硬磁-软磁-硬磁三层膜体系的不可逆交换弹性反磁化过程

采用一维原子链模型研究了反铁磁耦合的硬磁/软磁/硬磁三层膜体系的反磁化过程. 研究结果表明,当考虑了软磁层的磁晶各向异性能后,软磁层厚度和界面交换耦合强度的改变都有可能导致软磁层的交换弹性反磁化过程由可逆过程转变为不可逆过程. 对软磁层很薄的体系,其反磁化过程是典型的可逆交换弹性反磁化过程. 然而,当软磁层厚度超过某一临界厚度t_c时,反磁化过程转变为不可逆的交换弹性反磁化过程. 软磁-硬磁界面交换耦合强度A_sh对反磁化行为也有很大的影响. 对于软磁层厚度小于临界厚度t_c的体系,也存在一个临界界面交换耦合强度A_sh^c. 当A_sh大于A_sh^c时,软磁层的反磁化过程是可逆的交换弹性反磁化过程;而当A_sh小于A_sh^c时,这一过程变为不可逆. 给出了体系的可逆与不可逆交换弹性反磁化过程随软磁层厚度和界面交换耦合强度变化的磁相图. 同时还研究了偏转场随软磁层厚度的变化关系. 关键词： 反铁磁耦合三层膜 交换弹性反磁化过程 反磁化机理 磁相图

Irreversible exchange-spring processes of antiferromagnetically exchange coupled hard-soft-hard trilayer structures

The demagnetization processes of antiferromagnetically exchange-coupled hard-soft-hard trilayer structures are studied based on the one-dimensional atomic chain model. It is found that when the magnetic anisotropy of soft layer is taken into account, the change of the soft layer thickness or the interfacial exchange coupling strength may lead to a transition from the reversible exchange-spring process to the irreversible process. For the trilayer structures with very thin soft layer, the demagnetization process exhibits typical reversible magnetic exchange-spring behavior. However as the thickness of soft layer increases, there appears a crossover point t_c, after which the process becomes irreversible. There occurs also a critical interfacial exchange constant A_sh^c, above which the exchange-spring process is reversible. When A_sh<A_sh^c, the irreversible exchange-spring process is realized. The phase diagrams of reversible and irreversible exchange-spring process are mapped in the plane of the interfacial exchange coupling A_sh and soft layer thickness N_s. The dependences of the bending field on the soft layer thickness for different interfacial exchange couplings are numerically examined.