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

Abstract

Dielectric anomaly observed in cubic Mn1.5Cr1.5O4 around ferrimagnetic ordering temperature (T (N)) 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 d ( xz ) and d (3z ) (2) (-r ) (2) 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 T (N.) We confirmed that these changes in structural parameters at T (N) 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.