J. Deisenhofer, S. Schaile, J. Teyssier, Zhe Wang, M. Hemmida, H. -A. Krug von Nidda, R. M. Eremina, M. V. Eremin, R. Viennois, E. Giannini, D. van der Marel, A. Loidl
We report on magnetization and electron spin resonance (ESR) measurements of Sr$_{2}$VO$_4$ with orthorhombic symmetry. In this dimer system the $V^{4+}$ ions are in tetrahedral environment and are coupled by an antiferromagnetic intra-dimer exchange constant $J/k_B \approx$ 100 K to form a singlet ground state without any phase transitions between room temperature and 2 K. Based on an extended-H\"{u}ckel-Tight-Binding analysis we identify the strongest exchange interaction to occur between two inequivalent vanadium sites via two intermediate oxygen ions. The ESR absorption spectra can be well described by a single Lorentzian line with an effective g-factor $g$ = 1.89. The temperature dependence of the ESR intensity is well described by a dimer model in agreement with the magnetization data. The temperature dependence of the ESR linewidth can be modeled by a superposition of a linear increase with temperature with a slope $\alpha$ = 1.35 Oe/K and a thermally activated behavior with an activation energy $\Delta/k_B$ = 1418 K, both of which point to spin-phonon coupling as the dominant relaxation mechanism in this compound.
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http://arxiv.org/abs/1210.1349
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