γ-Fe2WO6 – A magnetodielectric with disordered magnetic and electronic ground states

Highlights: • This letter presents the first comprehensive investigation of the high temperature polymorph of the Fe-W-O series, using magnetic, thermodynamic and dielectric measurements. • Our observations indicate that this system exhibits a series of magnetic transitions as a function of temperature, with all of them being associated with a finite magneto-dielectric effect. • Moreover, our magnetization and dielectric loss measurements also indicate that this system appears to have an inhomogeneous magnetic and electric ground state – as evidenced by glass like signatures in both sectors. • This is reminiscent of features seen in the mixed valent manganites, which have attracted wide attention in the past. • This suggests that the Fe-W-O based systems could also offer an interesting playground for the investigation of phenomena like electronic phase separation. • With magneto-dielectricity being of topical interest considering the potential utility of this effect in a number of practical applications, the observation of a finite magneto-dielectric effect in γ-Fe₂WO₆ extending up-to room temperatures is also significant. The magnetic, thermodynamic and dielectric properties of the $\gamma$-Fe₂WO₆ system is reported. Crystallizing in the centrosymmetric Pbcn space group, this particular polymorph exhibits a number of different magnetic transitions, all of which are seen to exhibit a finite magneto-dielectric coupling. At the lowest measured temperatures, the magnetic ground state appears to be glass-like, as evidenced by the waiting time dependence of the magnetic relaxation. Also reflected in the frequency dependent dielectric measurements, these signatures possibly arise as a consequence of the oxygen non-stoichiometry, which promotes a disordered magnetic and electronic ground state.