交换弹簧磁性多层膜的磁矩取向及磁滞回线的解析研究

The analytical investigation of the magnetic orientation and hysteresis loop in exchange-spring magnetic multilayers

本文以界面交换耦合常数Ji和软磁相厚度Ls为主要参变量,研究了易轴与膜面平行情况下的Nd2Fe14B/α-Fe磁性多层膜的磁矩随外场变化的取向及磁滞回线,并得到了成核场的解析公式.分析发现,Ji对磁矩取向、钉扎场和矫顽力机理有着较大的影响.当Ls较小时,钉扎场等于成核场,随着Ji的减小,矫顽力机理由成核变为钉扎;当Ls较大时,矫顽力机理随Ji的改变情况恰好相反.钉扎场与成核场发生分离的临界厚度随着Ji的减小而减小.退耦合作用情况下,刚性磁体(rigidcomposite)只有在Ls非常小时才会出现.退耦合作用导致软硬磁相交界面出现角度突变,使得复合多层膜由单相行为向两相行为转变,同时使得成核场减小,并且当Ls较大时导致钉扎场增加.

Using the interface coupling constant Ji and the soft layer thickness Ls as the main variables,the changes of the magnetic moments with the applied field and the hysteresis loops of Nd2Fe14B /α-Fe trilayers,whose easy axes of all layers lie in the film plane,have been investigated. Analysis shows that Ji has significant influence on the magnetic orientation, the pinning field HP and the coercivity mechanism. When Ls is small,HP equals to HN,where the coercivity mechanism transforms from nucleation to pinning as Ji decreases,whereas for large Ls this trend is reversed. The critical thickness,at which the nucleation field and pinning field detaches,decreases as Ji decreases. When the reduced exchange coupling is considered,the rigid composite magnet appears only when Ls is very small. The reduced exchange coupling leads to a sudden change of angle of magnetization at the interface,which results in the change of the behavior of the trilayers from the single-phase one to the two-phase one and in the decrease of HN,whereas HP increases when Ls is larger.