交换偏置双层膜中的反铁磁自旋结构及其交换各向异性  

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

作　　者：许小勇[1] 潘靖[1] 胡经国[1] 

机构地区：[1]扬州大学物理科学与技术学院,扬州225002

出　　处：《物理学报》2007年第9期5476-5482,共7页Acta Physica Sinica

基　　金：国家自然科学资金(批准号:10347118);江苏省高校自然科学基金(批准号:2006KJB140133)资助的课题.~~

摘　　要：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≤0.1σw(反铁磁畴壁能量σw)时,系统有正交换偏置,若J2>0.1σw,系统出现增强的矫顽场,但无交换偏置.当界面处存在二次耦合下,其双二次耦合可削弱甚至消除交换偏置,而总增强矫顽场.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 =0.1σw（σw 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.

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 

分 类 号：O484.43[理学—固体物理]