An EPR study of the luminescent triplet state of VO3−4 in YVO4 and YP0.96V0.04O4 single crystals at 1.2 K

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Abstract
An EPR study with optical detection is reported of the luminescent triplet state of the VO3−4 ion in single crystals of YVO4 and YPO4 doped with VO3−4 . The experiments in an external magnetic field and in zero field can be fitted by a spin Hamiltonian for an orbitally nondegenerate triplet state. Signals originate from four symmetry‐related species; the directions of the principal axes of the four ZFS tensors indicate a lowering of symmetry of the VO3−4 ion in accordance with a static Jahn–Teller effect by which the tetrahedron tends to a trigonal pyramid on excitation. For YVO4 the ZFS parameters are: ‖D‖=0.58±0.04, ‖E‖=13.72±0.04 GHz, and for YPO4: ‖D‖=1.12±0.04, ‖E‖=12.98±0.04 GHz (z axis∥V–O bond and y⊥ac or bc crystallographic plane). For the mixed crystal the lifetimes of the individual spin levels were determined: τx=0.35, τy=3.3, τz=1.4 ms.