Seo J W, Fullerton E E, Nolting F, Scholl A, Fompeyrine J, Locquet J-P
Department Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44-bus 2450, B-3001 Heverlee, Belgium.
J Phys Condens Matter. 2008 Jul 2;20(26):264014. doi: 10.1088/0953-8984/20/26/264014. Epub 2008 Jun 9.
Antiferromagnetic (AFM) orthoferrites are interesting model systems for exploring the correlation between their crystalline and AFM domains and the resulting exchange bias when coupled to a ferromagnetic layer. In particular, LaFeO(3) (LFO) has a Néel temperature, T(N) = 740 K, which is the highest in the orthoferrite family. The recent developments of synchrotron radiation-based photoelectron emission microscopy (PEEM) have provided the possibility of studying AFM domain structures as well as the magnetic coupling between the AFM and the adjacent ferromagnetic (FM) layer, domain by domain. Thin films of LFO have proved excellent candidates for such studies because their AFM domains are well defined and large enough to be readily imaged by PEEM. This paper reviews the growth, structural and magnetic properties of LFO thin films as well as exchange coupling to a FM layer. The strong correlation between structural and AFM domains in this material allows us to investigate the exchange coupling as a function of the domain configuration, which can be changed by using different substrate material and substrate orientation. A significant increase of the exchange bias field by a factor of about 10 was obtained when LFO was diluted with Ni atoms in the volume part. In this sample, the structural domain boundary became corrugated due to substitutional defects. Our results indicate that the details of the precise domain boundary configuration strongly affect the exchange coupling.
反铁磁（AFM）正铁氧体是用于探索其晶体和AFM畴之间的相关性以及与铁磁层耦合时产生的交换偏置的有趣模型系统。特别是，LaFeO(3)（LFO）具有奈尔温度T(N)=740 K，这是正铁氧体系列中最高的。基于同步辐射的光电子发射显微镜（PEEM）的最新发展提供了逐个畴研究AFM畴结构以及AFM与相邻铁磁（FM）层之间磁耦合的可能性。LFO薄膜已被证明是进行此类研究的优秀候选材料，因为它们的AFM畴定义明确且足够大，便于通过PEEM成像。本文综述了LFO薄膜的生长、结构和磁性以及与FM层的交换耦合。这种材料中结构畴和AFM畴之间的强相关性使我们能够研究作为畴配置函数的交换耦合，畴配置可以通过使用不同的衬底材料和衬底取向来改变。当LFO在体积部分用Ni原子稀释时，交换偏置场显著增加了约10倍。在这个样品中，由于替代缺陷，结构畴边界变得起伏不平。我们的结果表明，精确的畴边界配置细节强烈影响交换耦合。
