Unraveling the magnetoelectric effect using electric field-controlled magnetic anisotropy: a theoretical study

Abstract

This article sheds light on the microscopic origin of the magnetoelectric effect, which could enable key control of magnetic properties by electric fields. In particular, it explains the influence of electric fields on the magnetic anisotropy of a Ni(II) complex characterized by significant uniaxial anisotropy and notable rhombicity. Our findings reveal that the electric field's effect on the axial anisotropy parameter primarily arises from atomic displacements, whereas for the rhombic parameter, it is driven by electronic structure changes. Notably, applying the electric field along the molecular axial direction-characterized by a substantial permanent dipole moment (~10 Debye)-produces a change in the axial parameter that is seven times weaker than when the field is applied orthogonally, where the dipole moment is nearly zero. We demonstrate that the magnetoelectric effect resulting from variations in the zero-field splitting (ZFS) parameters is dictated by the nature of electronic excitations between orbitals that determine the magnitude of the magnetic anisotropy, rather than by the dipole moment's magnitude. As this behavior can be rationalized using crystal field theory, it offers a general principle that can help the design of molecules with predictable magnetoelectric responses.