Magnetodielectric coupling in Mn3O4

TL;DR

This study explores the magnetodielectric effects in Mn3O4, revealing how magnetic transitions influence dielectric properties and suggesting spin-phonon coupling as a key mechanism.

Contribution

It provides new insights into the magnetodielectric coupling in Mn3O4, combining experimental measurements with band structure calculations to understand the underlying mechanisms.

Findings

Dielectric constant decreases at magnetic transitions without magnetic field.

Magnetic field enhances dielectric constant at intermediate transition.

Mn3O4 is a ferrimagnetic semiconductor with strong Jahn-Teller distortion.

Abstract

We have investigated the dielectric anomalies associated with spin ordering transitions in the tetragonal spinel Mn$_3$O$_4$, using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering transitions in Mn$_3$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, Mn$_3$O$_4$ corresponds to a semiconductor with no orbital degeneracy due to strong Jahn-Teller distortion.