Electric Field Shift in Electron Paramagnetic Resonance forMn2+in CaWO4

Abstract

The electric field shifts in paramagnetic resonance of ${\mathrm{Mn}}^{2+}$ in CaW${\mathrm{O}}_4$ have been measured and the components of the third-rank tensor defining the change in the spin Hamiltonian have been derived from the measurement. The theoretical determination of the tensor elements using an "equivalent even field" technique gave values at least a factor of 10 too small. Two possible mechanisms for the anomalously large shifts observed in ${\mathrm{Mn}}^{2+}$ are discussed, one based on the explicit mixture of odd states into the ground manifold, the other on ionic motion. The hypothesis that the first of these mechanisms is responsible for the large shifts implies that the normal $D$ term of ${\mathrm{Mn}}^{2+}$ is CaW${\mathrm{O}}_4$ depends significantly on the strength of the odd crystal field.