Magneto-Optical Study of the Spin-Lattice Relaxation ofFe3+in MgO

Abstract

A double-resonance method, using the combination of magnetic circular dichroism (MCD) and electron spin resonance (ESR), is used to measure the ratio of the two independent spin-phonon tensor components $G_{11}$ and $G_{44}$. For ${\mathrm{Fe}}^{3+}$ in MgO, the obtained ratio $\frac{G_{11}}{G_{44}}$ is compared with both the ultrasonic method of Shiren and the static method of Watkins and Feher. An analysis of the double-resonance data indicates that the pattern is extremely sensitive to the form of the spin operator used for the spin-phonon interaction term. It is found that the proposed form gives a good fit to the experimental data. An added feature of the double-resonance method is the ability to correlate directly the optical absorption bands of ${\mathrm{Fe}}^{3+}$ in MgO with its well-known electron spin resonance. It has been found that both the 4.4- and the 5.7-eV charge-transfer optical-absorption bands originate from the ${\mathrm{Fe}}^{3+}$ ground state.