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Magnetic transition and orbital degrees of freedom in vanadium spinels

Hirokazu Tsunetsugu·Yukitoshi Motome
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Abstract

We propose a scenario for the two phase transitions in $A$V$_2$O$_4$ ($A$=Zn, Mg, Cd), based on an effective spin-orbital model on the pyrochlore lattice. At high temperatures, spin correlations are strongly frustrated due to the lattice structure, and the transition at $\sim$50 [K] is an orbital order, supported by Jahn-Teller lattice distortion. This orbital order introduces spatial modulation of spin exchange couplings depending on the bond direction. This partially releases the frustration, and leads to a spin order at $\sim$40 [K]. We also study the stable spin configuration by taking account of third-neighbor exchange couplings and quantum fluctuations. The result is consistent with the experimental results.

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Hirokazu Tsunetsugu, Yukitoshi Motome. 2003-05-12. Magnetic transition and orbital degrees of freedom in vanadium spinels. https://doi.org/10.1103/physrevb.68.060405

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