反铁磁四面体分子Ni4Mo12的非弹性中子散射研究和哈伯德模型描述
Inelastic neutron scattering study and Hubbard model description of the antiferromagnetic tetrahedral molecule Ni4Mo12
摘要：
用惯性干涉仪（INS）研究了Ni（II）四聚体自旋团簇Ni 4 Mo 12，用一个非常一般的自旋哈密顿量对数据进行了广泛的分析，其中包括反铁磁海森堡相互作用、双二次2-自旋和3-自旋相互作用、单离子磁各向异性和Dzyaloshinsky-Moriya相互作用.一些实验观察到的功能在INS光谱可以重现，但是，一个功能在1.65毫电子伏抵制所有的努力。这支持了自旋哈密顿方法不足以描述Ni 4 Mo 12磁性的结论。自旋哈密顿量中的各向同性项可以在半填充的哈伯德模型的强耦合展开中得到。因此，详细的理论研究的哈伯德模型进行，使用分析以及数值技术。我们仔细分析了它在分子自旋团簇中的应用能力和局限性。作为主要结果，发现哈伯德模型也不能适当地解释Ni 4 Mo 12中的磁性。模型的扩展也进行了讨论。
英文摘要：
The tetrameric Ni(II) spin cluster Ni4Mo12 has been studied by INS. The data were analyzed extensively in terms of a very general spin Hamiltonian, which includes antiferromagnetic Heisenberg interactions, biquadratic 2-spin and 3-spin interactions, a single-ion magnetic anisotropy, and Dzyaloshinsky-Moriya interactions. Some of the experimentally observed features in the INS spectra could be reproduced, however, one feature at 1.65 meV resisted all efforts. This supports the conclusion that the spin Hamiltonian approach is not adequate to describe the magnetism in Ni4Mo12. The isotropic terms in the spin Hamiltonian can be obtained in a strong-coupling expansion of the Hubbard model at half-filling. Therefore detailed theoretical studies of the Hubbard model were undertaken, using analytical as well as numerical techniques. We carefully analyzed its abilities and restrictions in applications to molecular spin clusters. As a main result it was found that the Hubbard model is also unable to appropriately explain the magnetism in Ni4Mo12. Extensions of the model are also discussed.
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