Orbital ordering and unfrustrated (π,0) magnetism from degenerate double exchange in the iron pnictides
Orbital ordering and unfrustrated (π,0) magnetism from degenerate double exchange in the iron pnictides
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DOI：
10.1103/physrevb.82.045125
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发表时间：
2010-02
影响因子：
3.7
通讯作者：
W. Lv;F. Kruger;P. Phillips
中科院分区：
文献类型：
--
作者：
W. Lv;F. Kruger;P. Phillips
的铁pnictides的磁激发内的简并双交换模型解释。局域磁矩自旋分别通过最近和次最近邻之间的超交换J{sub 1}和J{sub 2}耦合，并通过铁磁Hund交换与简并d{sub xz}和d{sub yz}轨道的巡游电子相互作用。后者通过优选地沿着铁磁自旋方向跳跃来稳定（π，0）条纹反铁磁性，这是由于出现的铁轨道顺序和所产生的动能增益。考虑到自旋的量子性质，我们计算了超交换和双交换两种情况下的磁激发谱。一个显着增加的自旋波的能量在竞争尼尔订购波矢量被发现，与最近的中子散射数据。的光谱拟合到一个自旋只有一个强的空间各向异性和额外的长程耦合沿着铁磁链模型。在一个实际的参数范围内，有效的耦合沿着链是负的对应于无阻挫条纹反铁磁性。
The magnetic excitations of the iron pnictides are explained within a degenerate double-exchange model. The local-moment spins are coupled by superexchanges J{sub 1} and J{sub 2} between nearest and next-nearest neighbors, respectively, and interact with the itinerant electrons of the degenerate d{sub xz} and d{sub yz} orbitals via a ferromagnetic Hund exchange. The latter stabilizes (π,0) stripe antiferromagnetism due to emergent ferro-orbital order and the resulting kinetic-energy gain by hopping preferably along the ferromagnetic spin direction. Taking the quantum nature of the spins into account, we calculate the magnetic excitation spectra in the presence of both, superexchange and double exchange. A dramatic increase in the spin-wave energies at the competing Neel ordering wave vector is found, in agreement with recent neutron-scattering data. The spectra are fitted to a spin-only model with a strong spatial anisotropy and additional longer-ranged couplings along the ferromagnetic chains. Over a realistic parameter range, the effective couplings along the chains are negative corresponding to unfrustrated stripe antiferromagnetism.