Analysis of the Spin Lattice Model for the Spin-Gapped Layered Compounds Na3Cu2SbO6 and Na2Cu2TeO6 on the Basis of Electronic Structur

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• 作者：Hyun-Joo Koo ; Myung-Hwan Whangbo
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：January 7, 2008
• 年：2008
• 卷：47
• 期：1
• 页码：128 - 133
• 全文大小：169K
• 年卷期：v.47,no.1(January 7, 2008)
• ISSN：1520-510X

文摘

The spin lattice model for the spin-gapped layered magnetic solids NaB>3Cu₂SbO₆ and Na₂Cu₂TeO₆ was examinedby evaluating the three spin exchange interactions of their Cu₂MO₆ (M = Sb, Te) layers in terms of spin dimeranalysis based on extended Hückel tight binding calculations and mapping analysis based on first principles densityfunctional theory electronic band structure calculations. For both compounds, our calculations show that the twostrongest spin exchange interactions, that is, the Cu-O···O-Cu super-superexchange (J₂) and the Cu-O-Cusuperexchange (J₁) interactions, form alternating chains that interact weakly through the Cu-O-Cu superexchange(J₃) interactions. The dominant one of the three spin exchange interactions is J₂, and it is antiferromagnetic inagreement with the fact that both of the compounds are spin gapped. For Na₃Cu₂SbO₆ and Na₂Cu₂TeO₆, thesuperexchange J₁ is calculated to be ferromagnetic, hence, leading to the alternating chain model in whichantiferromagnetic and ferromagnetic spin exchange interactions alternate. This picture does not agree with therecent experimental analysis, which showed that the temperature-dependent magnetic susceptibilities of bothcompounds should be described by the alternating chain model in which two antiferromagnetic spin exchangeinteractions of different strengths alternate.