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arXiv 1208.0637cond-mat.str-el
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自旋态跃迁驱动的Sr2-xLaxCoO4的金属-绝缘体相变

Metal-insulator transition in Sr2-xLaxCoO4 driven by spin-state transition

Hua Wu

摘要:

我们寻求起源的Sr 2-xLaxCoO 4中的金属-绝缘体转变,使用电子相关校正的密度泛函计算。结果表明,Sr_2CoO_4处于中间自旋(IS)态,Co ~(4+)3d-O ~(2 p)杂化是其铁磁金属性的主要原因.然而,当La掺杂时,在Sr 1.5La 0.5CoO 4:IS-Co 4 + x 2 + 1 e--> LS-Co 4 + + HS-Co 3+中发生自旋态转变(LS:低自旋; HS:高自旋)。然后自旋态转变通过自旋阻断抑制电子跳跃,并引起Sr1.5La0.5CoO4的绝缘行为。相应的超交换解释了它的铁磁性。因此,自旋态可以提供一种调节材料性质的方法。

英文摘要:

We sought the origin of the metal-insulator transition in Sr2-xLaxCoO4, using electron-correlation corrected density functional calculations. Our results show that Sr2CoO4 is in an intermediate-spin (IS) state and a strong Co4+ 3d-O 2p hybridization is responsible for its ferromagnetic metallicity. Upon La doping, however, a spin-state transition occurs in Sr1.5La0.5CoO4: IS-Co4+ x 2 + 1e --> LS-Co4+ + HS-Co3+ (LS: low spin; HS: high spin). Then the spin-state transition suppresses an electron hopping via a spin-blockade and gives rise to the insulating behavior of Sr1.5La0.5CoO4. A corresponding superexchange accounts for its ferromagnetism. Thus, spin state could provide a way to tune materials properties.

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