Theory of Successive Transitions in Vanadium Spinels and Order of Orbitals and Spins(Yukawa International Seminar 2004 (YKIS2004) Physics of Strongly Correlated Electron Systems)

概要

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We have theoretically studied successive transitions in vanadium spinel oxides with (t_<2g>)^2 electron configuration. These compounds show a structural transition at〜50K and an antiferromagnetic transition at〜40K. Since threefold t_<2g> orbitals of vanadium cations are occupied partially and vanadiums constitute a geometrically-frustrated pyrochlore lattice, the system provides a particular example to investigate the interplay among spin, orbital and lattice degrees of freedom on frustrated lattice. We examine the models with the Jahn-Teller coupling and/or the spin-orbital superexchange interaction, and conclude that keen competition between these two contributions explains the thermodynamics of vanadium spinels. Effects of quantum fluctuations as well as relativistic spin-orbit coupling are also discussed.
理論物理学刊行会の論文
2006-02-06