Investigations of the temperature dependence of the electron paramagnetic resonance g-factor for the MgO:Cr3+ crystal

Detailed theoretical studies of the temperature dependence of EPR g-factor for the MgO:Cr3+ crystal have been made by considering both the static contribution due to the thermal expansion of crystal and the vibrational contributions due to the electron-phonon (including the acoustic and optical phonons) interaction. The static contribution is calculated from the macroscopic thermodynamic method and the microscopic crystal-field method. The results from both methods are close to each other, suggesting that the two methods are applicable to studies of temperature dependence of the g-factor. The vibrational contribution due to acoustic phonons is obtained by using a Debye model for the lattice vibrations, and that due to optical phonons is calculated by use of a single-frequency model. The calculated results show that, for the g(T)-factors at various temperatures, the static contribution is dominant; however, for the temperature dependence of the g-factor, i.e. dg/dT, the vibrational contributions are large and should be taken into account.