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.