Ir（001）上Fe双原子链的结构驱动磁态跃迁
Structurally-driven magnetic state transition of biatomic Fe chains on Ir(001)
摘要：
利用第一性原理计算，我们证明了在5 × 1重构Ir（001）表面沟槽中生长的双原子Fe链的磁交换相互作用和磁晶各向异性敏感地依赖于Fe原子的原子排列.两种结构配置已被认为是建议从最近的实验。它们的不同之处在于局部对称性和双原子Fe链两股之间的间距。由于这两种构型的总能量非常接近，它们在实验中可能共存。我们已经研究了共线铁磁和反铁磁的解决方案，以及一个共线的状态，两个时刻在一个方向和一个在相反的方向（向上-向下-向上状态）。对于链间距较小的结构，链间存在较强的交换作用，铁磁态在能量上是有利的。在间距较大的结构中，两股线几乎是磁解耦的，并沿链呈现反铁磁有序。在这两种情况下，由于与Ir衬底的杂交，沿着链轴的交换相互作用相对于独立的双原子铁链较小。Fe链的易磁化轴也随着结构的变化而变化，对于间距小的铁磁链，易磁化轴在面外，而对于间距大的反铁磁链，易磁化轴沿链轴。计算的扫描隧道显微镜图像和光谱表明实验区分两种结构和磁性配置的可能性。
英文摘要：
Using first-principles calculations, we demonstrate that the magnetic exchange interaction and the magnetocrystalline anisotropy of biatomic Fe chains grown in the trenches of the 5x1 reconstructed Ir(001) surface depend sensitively on the atomic arrangement of the Fe atoms. Two structural configurations have been considered which are suggested from recent experiments. They differ by the local symmetry and the spacing between the two strands of the biatomic Fe chain. Since both configurations are very close in total energy they may coexist in experiment. We have investigated collinear ferro- and antiferromagnetic solutions as well as a collinear state with two moments in one direction and one in the opposite direction (up-down-up-state). For the structure with a small interchain spacing, there is a strong exchange interaction between the strands and the ferromagnetic state is energetically favorable. In the structure with larger spacing, the two strands are magnetically nearly decoupled and exhibit antiferromagnetic order along the chain. In both cases, due to hybridization with the Ir substrate the exchange interaction along the chain axis is relatively small compared to freestanding biatomic iron chains. The easy magnetization axis of the Fe chains also switches with the structural configuration and is out-of-plane for the ferromagnetic chains with small spacing and along the chain axis for the antiferromagnetic chains with large spacing between the two strands. Calculated scanning tunneling microscopy images and spectra suggest the possibility to experimentally distinguish between the two structural and magnetic configurations.
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