| The steady interest in frustrated magnets with degenerate orbitals is driven by the continuous discovery of unusual magnetic and orbital orderings resulting from an intricate interplay between frustration, lattice distortions, spin-orbit interaction, and electron correlations. Here we discuss the magnetic and orbital ordering in the family of vanadium spinels AV2O4 with A = Mn, Zn, Cd, Mg. Although these vanadates are insulators at low temperatures, recent experimental studies show that none of these compounds satisfy the phenomenological Bloch's relation that must hold in the deep Mott regime. We present analytical models and numerical simulations that take into account the partial electron delocalization in the intermediate-coupling regime of Mott insulators. In particular, we show that the special magnetic ordering in vanadium spinels leads to a rapid suppression of orbital order due to enhanced charge fluctuations along ferromagnetic bonds. |
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