Department of Applied Science, College of William and Mary, 251 Jamestown Road, Williamsburg, Virginia 23187, USA.
Nat Nanotechnol. 2013 Jun;8(6):438-44. doi: 10.1038/nnano.2013.94. Epub 2013 Jun 2.
The ferromagnet/oxide interface is key to developing emerging multiferroic and spintronic technologies with new functionality. Here we probe the Fe/MgO interface magnetization, and identify a new exchange bias phenomenon manifested only in the interface spin system, and not in the bulk. The interface magnetization exhibits a pronounced exchange bias, and the hysteresis loop is shifted entirely to one side of the zero field axis. However, the bulk magnetization does not, in marked contrast to typical systems where exchange bias is manifested in the net magnetization. This reveals the existence of an antiferromagnetic exchange pinning layer at the interface, identified here as FeO patches that exist even for a nominally 'clean' interface. These results demonstrate that atomic moments at the interface are non-collinear with the bulk magnetization, and therefore may affect the net anisotropy or serve as spin scattering sites. We control the exchange bias magnitude by varying the interface oxygen concentration and Fe-O bonding.
铁磁/氧化物界面是开发新兴多铁性和自旋电子技术的关键，这些技术具有新的功能。在这里，我们探测了 Fe/MgO 界面的磁化强度，并确定了一种新的交换偏置现象，这种现象仅在界面自旋系统中表现出来，而不在体相中表现出来。界面磁化强度表现出明显的交换偏置，磁滞回线完全偏移到零场轴的一侧。然而，体磁化强度却没有，这与典型的在净磁化强度中表现出交换偏置的系统形成鲜明对比。这表明在界面处存在反铁磁交换钉扎层，在这里被确定为即使在名义上“清洁”的界面上也存在的 FeO 小贴片。这些结果表明，界面处的原子磁矩与体磁化强度不成共线，因此可能会影响净各向异性或作为自旋散射点。我们通过改变界面氧浓度和 Fe-O 键合来控制交换偏置的大小。
