提出了一个讨论铁磁/反铁磁双层膜中的交换偏置及矫顽场温度特性的物理模型,该模型,假设铁磁层为具有单轴各向异性的单畴膜而反铁磁层由许多相互独立具有多晶各向异性的颗粒组成,其温度依赖性主要来源于系统态的热不稳定,包括反铁磁颗粒易轴取向的热涨落和相关磁学量的温度依赖性等.计算结果表明其交换偏置随温度的增加非线性地减少而其矫顽场在体阻截温度处达极大值,且其体阻截温度随反铁磁颗粒粒径的增加而增加.我们的计算结果和相关实验结果一致.通过本文的讨论,我们建议通过铁磁膜耦合上大粒径硬反铁磁颗粒膜可获得高交换偏置、低矫顽场且近独立于温度的相关磁学器件.
A available model is presented for the temperature dependence of exchange bias and coercivity inferromagnetic (FM) and antiferronagnetic (AFM) bilayers. In this model, the FM layer is consideredas a single domain with uniaxial anisotropy while the AFM layer is treated as many independent AFMgrains with polystalline anisotropy. The temperature dependence comes from the thermal instability of thesystem state, including the thermal fluctuation of orientations of easy axes of AFM grains and the temper-ature modulated relative magnetic parameters. These results show that, the exchange bias nonlinearlydecreases with increasing temperature but there is a peak for the coercivity. The block temperature in-creases with size increase of AFM grains. These results are in good agreement with experimental resultsqualitatively. Based on our discussion, we can conclude that FM layer coupled by a hard AFM layercomprised by large size of AFM grain may be very applicable to design magnetic devices almost indepen-dent of temperature with high exchange bias and low coercivity.
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