Abstract Incorporation of the V3+ and V4+ ions into the yttrium aluminum garnet Y3Al5O12 (YAG) lattice has been studied by the correlated optical absorption and electron paramagnetic resonance (EPR) measurements.… Click to show full abstract
Abstract Incorporation of the V3+ and V4+ ions into the yttrium aluminum garnet Y3Al5O12 (YAG) lattice has been studied by the correlated optical absorption and electron paramagnetic resonance (EPR) measurements. Only the V3+ ions at both octahedral and tetrahedral aluminum sites are found in as-grown crystals. However, annealing in air leads to the transformation of the V3+ to V4+, whereas annealing in the hydrogen atmosphere remains the V3+ concentration almost unchanged. Spin Hamiltonian parameters of the V3+ and V4+ ions at the tetrahedral sites including the zero field splitting and 51V hyperfine constants are determined using high-frequency, up to 300 GHz, EPR measurements. By using the spin Hamiltonian parameters, the ground state energy levels splitting of the V3+ and V4+ ions were calculated in the framework of the crystal field theory. The g and hyperfine tensors suggest that electron density around the tetrahedral V3+ ion is distributed strongly inhomogeneously resulting also in large (40%) reduction of the spin-orbit coupling constant whereas the tetrahedral V4+ ion exhibits weaker covalent bounding with surrounding ligands. Furthermore, the obtained EPR data on vanadium ions allow to improve identification of the optical absorption peaks in YAG:V crystals.
               
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