Key Laboratory of Magnetism and Magnetic Materials of the Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou 730000, P. R. China.
Nanoscale. 2018 Dec 7;10(45):21499-21508. doi: 10.1039/c8nr07642a. Epub 2018 Nov 14.
Exchange-biased magnetic heterostructures have become one of the research frontiers due to their significance in enriching the fundamental knowledge in nanomagnetics and promising diverse applications in the information industry. However, the physical origin of their exchange bias effect is still controversial. A key reason for this is the lack of unequivocal observations of interface growth. In this work, we fill this gap by experimentally imaging the ferrimagnetic/diamagnetic interfaces of Au-FeO nanodimers at the atomic level. A different physical mechanism from the reported mechanisms is found based on the atomic-resolution observation of their interfacial structure and electronic states, which reveals that the antiferromagnetic and ferromagnetic interactions of the formed weak/strong ferrimagnetic bilayer are responsible for the intrinsic exchange-bias origin in Au-FeO nanodimers. The theoretical quantitative analysis of the exchange bias shift based on the observed interfacial occupation model agrees well with the experimental value for the exchange bias effect, strongly verifying the proposed exchange-bias mechanism.
交换偏置磁性异质结构由于在丰富纳米磁性基本认识和在信息产业中有多种潜在应用而成为研究前沿之一。然而，其交换偏置效应的物理起源仍存在争议。造成这种情况的一个关键原因是缺乏对界面生长的明确观察。在这项工作中，我们通过实验在原子水平上对 Au-FeO 纳米二聚体的亚铁磁/非磁界面进行成像，填补了这一空白。基于对其界面结构和电子态的原子分辨率观察，发现了与已报道机制不同的物理机制，表明形成的弱/强亚铁磁双层的反铁磁和铁磁相互作用是 Au-FeO 纳米二聚体中固有交换偏置起源的原因。基于观察到的界面占据模型对交换偏置位移的理论定量分析与实验交换偏置效应值吻合较好，强烈验证了所提出的交换偏置机制。
