Electron spin resonance and exchange paths in the orthorhombic dimer system Sr2VO4

TL;DR

This study investigates the magnetic properties and exchange interactions in Sr2VO4 using ESR and magnetization measurements, revealing a strong antiferromagnetic dimer system with significant spin-phonon coupling.

Contribution

It provides detailed ESR and magnetization analysis of Sr2VO4, identifying the dominant exchange paths and relaxation mechanisms in this orthorhombic vanadium oxide dimer system.

Findings

Strong antiferromagnetic intra-dimer exchange constant (~100 K)

ESR spectra well described by a single Lorentzian with g=1.89

Spin-phonon coupling dominates relaxation mechanisms

Abstract

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.