Understanding the correlation between orbital degree of freedom, lattice-striction and magneto-dielectric coupling in ferrimagnetic Mn1.5Cr1.5O4.

Dielectric anomaly observed in cubic Mn1.5Cr1.5O4around ferrimagnetic ordering temperature (TN) suggests a possible magneto-dielectric coupling in the system. This report confirms the presence of a weak but significant magneto-dielectric coupling in the system. Theab initiocalculations show a band gap of around 1.2 eV, with Fermi-level closer to the conduction band. The major features of conduction band nearest to the Fermi-level correspond todxzandd3z2-r2orbitals of Mn3+ion. Temperature-dependent neutron diffraction results show a rapid decay in structural parameters (lattice-striction and transition metal-oxygen bond length) aroundTN.We confirmed that these changes in structural parameters atTNare not related to structural transition but the consequences of orbital-ordering of Mn3+. The rapid decay in transition metal-oxygen bond length under internal magnetism of the system shows that magnetism could certainly manipulate the electric dipole moment and hence the dielectric constant of the system. Magneto-striction acts as a link between magnetic and dielectric properties.