Understanding the Correlation Between Orbital Degree of Freedom, Lattice-Striction and Magneto-Dielectric Coupling in Ferrimagnetic Mn1.5Cr1.5O4

Dielectric anomaly observed in cubic Mn1.5Cr1.5O4 around 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. The ab initio calculations 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 to dxz and d3z2-r2 orbitals of Mn3+ ion. Temperature-dependent neutron diffraction results show a rapid decay in structural parameters (lattice-striction and transition metal-oxygen bond length) around TN. We confirmed that these changes in structural parameters at TN are 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.