铁磁球/反铁磁纳米体系磁滞回线的Monte Carlo模拟

Hysteresis Loops of FM Core/AFM Systems:A Monte Carlo Study

利用经典Heisenberg模型和Monte Carlo方法研究外磁场和反铁磁磁晶各向异性、交换相互作用对铁磁球均匀嵌入到反铁磁基体中的铁磁/反铁磁纳米体系磁滞回线的影响.模拟结果显示,外加反向最大磁场不同时,磁滞回线形状不同.当磁场正向增加时,体系的磁化强度会产生一个跃变,但跃变高度与反向场最大值无关.反铁磁磁晶各向异性越大,体系的交换偏置现象越明显,且磁化强度回到饱和值所需的外磁场越大.随着反铁磁基体交换相互作用的增大,在正向和负向磁场区域还可能出现新的磁滞现象.

Monte Carlo method is used to study hysteresis loops of FM/AFM systems with FM core embedded in an AFM matrix in a classical Heisenberg model. Magnetocrystalline anisotropy and exchange interaction are considered. It indicates that the shape of hysteresis loops changes with reverse maximal external field. The magnetization shows a jumping transition to metastable equilibrium with an increasing of external fields along positive z axis. The jumping range is independent of reverse maximal external field. With an increasing of AFM magnetocrystalline anisotrepy, exchange bias is obvious and larger external fields are needed for magnetization saturation. With an increasing of AFM exchange interaction, new hysteresis loops may appear in positive and negative external fields.