Probing the magnetic excitations of a frustrated spinel pyrochlore

Orateur : Elisa WHEELER (ILL)

Spin systems on pyrochlore lattices can exhibit several exotic magnetic properties due to the macroscopic degeneracy caused by the geometrical frustration of the lattice. The pyrochlore lattice is a network of corner sharing tetrahedral. If spins on this lattice are connected by antiferromagnetic interactions, it forms a three-dimensionally frustrated magnet. The Vanadium spinels AV2O4, where A is a diamagnetic ion, realize such a system. The magnetic V3+-ions are antiferromagnetically coupled and sit at vertices of a pyrochlore network. The magnetic V3+ (S=1) has two electrons occupying the triply degenerate 3d-shell t2g orbitals. Therefore this is a low spin system in comparison to Rare earth pyrochlore systems and as such is expected to accentuate quantum effects. In this talk, I will discuss the magnetic excitations of frustrated low-spin systems and, in particular, the vanadium spinels both in their structurally distorted tetragonal phase and in their higher-temperature cubic ph ase. This is a large single crystal study based on neutron inelastic scattering measurements.

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