Work

Electron spin resonance and exchange paths in the orthorhombic dimer system Sr 2 VO 4

Year: 2012

Type: article

Abstract: We report on susceptibility and electron spin resonance (ESR) measurements at X- and Q-band frequencies of Sr${}_{2}$VO${}_{4}$ with orthorhombic symmetry. In this dimer system, the ${\text{V}}^{4+}$ ions are in tetrahedral environment and are coupled by an antiferromagnetic intradimer exchange constant $J/{k}_{B}\ensuremath{\approx}$ 100 K to form a singlet ground state without any phase transitions between room temperature and 2 K. Based on an extended H\"uckel 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 fitted by a single Lorentzian line and the temperature dependence of the ESR intensity, and the dc susceptibility can be modeled by using the Bleaney-Bowers approach for independent dimers. The temperature dependence of the ESR linewidth at X-band frequency can be modeled by a superposition of a linear increase with temperature with a slope $\ensuremath{\alpha}$ $=$1.35 Oe/K and a thermally activated behavior with an activation energy $\ensuremath{\Delta}/{k}_{B}$ $=$1418 K, both of which point to spin-phonon coupling as the dominant relaxation mechanism in this compound.

Source: Physical Review B

DOI: 10.1103/physrevb.86.214417