Electronic structure and microscopic model of V₂GeO₄F₂-a quantum spin system with S= 1

Abstract

We present first-principles density functional calculations and downfolding studies of the electronic and magnetic properties of the oxide-fluoride quantum spin system V₂GeO₄F₂. We discuss explicitly the nature of the exchange paths and provide quantitative estimates of magnetic exchange couplings. A microscopic modelling based on analysis of the electronic structure of this systems puts it in the interesting class of weakly coupled alternating chain S = 1 systems. Based on the microscopic model, we make inferrences about its spin excitation spectra, which needs to be tested by rigorous experimental study.