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

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 α = 1.35 Oe/K and a thermally activated behavior with an activation energy �/k B = 1418 K, both of which point to spin-phonon coupling as the dominant relaxation mechanism in this compound.