arXiv 0903.23482009-03-13cond-mat.mtrl-sci

Ir（100）表面Fe双链结构与磁性的关系

Connection Between Magnetism and Structure in Fe Double Chains on the Ir(100) Surface

R. Mazzarello, E. Tosatti

备注：: to appear on PRB
发表信息：: Phys. Rev. B 79, 134402 (2009)
DOI：: 10.1103/PhysRevB.79.134402

摘要：

纳米尺度系统的磁性基态，如Fe双链，最近被证明是在Fe沉积在Ir（100）上的早期阶段形成的，通常是不平凡的。利用从头计算密度泛函理论，我们发现在Ir（100）上沉积后，对于所有的实验相关的双链结构，铁的直铁磁（FM）态都是不利的。只要自旋轨道耦合（SOC）被忽略，双链的最低能量状态通常是反铁磁（AFM），一个状态，似乎占上风的FM状态，由于Fe-Ir杂化。连续列入SOC增加了另外两个元素，即磁晶各向异性，和Dzyaloshinskiii-Moriya（DM）自旋-自旋相互作用，前者稳定共线AFM状态，第二个有利于长周期自旋调制。我们发现，各向异性是最重要的，当双链吸附在部分解构的Ir（100）-一个状态，我们发现是大大低于任何重建的结构的能量-因此，在这种情况下，Fe双链应保持共线AFM。或者，当相同的Fe双链以亚稳态吸附在（5 × 1）完全重构的Ir（100）表面上时，FM-AFM能量差大大减小，并且DM相互作用预计占优势，可能产生螺旋自旋结构。

英文摘要：

The magnetic ground state of nanosized systems such as Fe double chains, recently shown to form in the early stages of Fe deposition on Ir(100), is generally nontrivial. Using ab initio density functional theory we find that the straight ferromagnetic (FM) state typical of bulk Fe as well as of isolated Fe chains and double chains is disfavored after deposition on Ir(100) for all the experimentally relevant double chain structures considered. So long as spin-orbit coupling (SOC) is neglected, the double chain lowest energy state is generally antiferromagnetic (AFM), a state which appears to prevail over the FM state due to Fe-Ir hybridization. Successive inclusion of SOC adds two further elements, namely a magnetocrystalline anisotropy, and a Dzyaloshinskii-Moriya (DM) spin-spin interaction, the former stabilizing the collinear AFM state, the second favoring a long-period spin modulation. We find that anisotropy is most important when the double chain is adsorbed on the partially deconstructed Ir(100) -- a state which we find to be substantially lower in energy than any reconstructed structure -- so that in this case the Fe double chain should remain collinear AFM. Alternatively, when the same Fe double chain is adsorbed in a metastable state onto the (5x1) fully reconstructed Ir(100) surface, the FM-AFM energy difference is very much reduced and the DM interaction is expected to prevail, probably yielding a helical spin structure.

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