交换偏置双层膜中的反铁磁自旋结构及其交换各向异性

研究了交换偏置双层膜中界面存在二次以及双二次交换耦合下反铁磁磁矩转动及其交换各向异性.结果表明，其反铁磁膜中的磁矩转动存在可逆“恢复行为”、不可逆“半转动行为”、不可逆“倒转行为”以及不可逆“半倒转行为”四种情形，四种情形的出现强烈地依赖于界面二次、双二次耦合以及反铁磁膜厚度.其中可逆恢复行为情况下，系统出现交换偏置，而不可逆的半转、半倒转以及倒转情形，系统不出现交换偏置.特别地,在界面处仅存在双二次耦合的情形下，其界面双二次耦合常数J₂≤0.1 σ关键词： 反铁磁自旋结构 交换各向异性 界面双二次耦合 交换偏置

Configuration of the antiferromagnetic magnetization and the exchange anisotropy in exchange-biased bilayers

The phases of the antiferromagnetic magnetization and the corresponding exchange bias and coercivity in exchange-biased bilayers(FM/AF) with interface quadratic and biquadratic exchange coupling have been studied comprehensively. The results show that there are four possible cases for the antiferromagnetic magnetization, namely the reversible recovering case, irreversible half-rotating case, irreversible reversing and irreversible half-reversing cases. However, the realization of the cases strongly depends on interface quadratic coupling, interface biquadratic coupling and AF thickness. In the reversible recovering case the exchange coupling between FM and AF results in the exchange bias, and there is no exchange bias in the other cases. Specially, for exchange-biased bilayers without interface quadratic coupling, there exists a critical value of the biquadratic coupling constant J_2crit=0.1σ_w(σ_w denotes AF domain wall energy), below which the positive exchange bias appears, otherwise there is no exchange bias, and the coercivity can be enhanced. For the FM/AF bilayers with interface quadratic and biquadratic coupling, the interface biquadratic coupling can weaken or eliminate the exchange bias, but always enhances the coercivity.