Magnetodielectric coupling inMn3O4

Abstract

We have investigated the dielectric anomalies associated with spin-ordering transitions in the tetragonal spinel ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering transitions in ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ lead to decreases in the temperature-dependent dielectric constant at zero applied field. Applying a magnetic field to the polycrystalline sample leaves these two dielectric anomalies practically unchanged, but leads to an increase in the dielectric constant at the intermediate spin-ordering transition. We discuss possible origins for this magnetodielectric behavior in terms of spin-phonon coupling. Band structure calculations suggest that in its ferrimagnetic state, ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$ corresponds to a semiconductor with no orbital degeneracy due to strong Jahn-Teller distortion.