The linear electric field effect on the electron paramagnetic resonance spectrum of Cu2+ ions in tetrahedral crystal fields

Abstract

A detailed theoretical discussion is given of the linear electric field effect occurring in electron paramagnetic resonance spectra from Cu²⁺ ions residing in tetrahedral crystal fields. Contributions from both the electronic effect and ionic effect components to the g shift are derived from basic principles for examples in which the trigonal or tetragonal distortions of the tetrahedron occur. The electronic effect arises because the ground state of Cu²⁺ consists of hybrids of 3d and 4p orbitals, while the ionic effect occurs because the change in crystal field due to the relative displacement of the ligand ions is linear in the applied electric field as a tetrahedron has no centre of symmetry. A measurable g shift is predicted for the trigonally distorted example only. From the theory discussed it is generally expected that the relative amounts of the two effects will vary considerably with both the host lattice and ion.