A theoretical investigation on the magneto-optical and magnetic properties of light rare-earth trifluorides ${\mathrm{CeF}}_3$, ${\mathrm{PrF}}_3$, and ${\mathrm{NdF}}_3$ is presented. The 0.6328-μm-wavelength Faraday rotation and susceptibility of these compounds in the temperature range 40–300 K have been calculated based on the quantum theory. The result shows that in the visible region the Faraday rotation is mainly caused by the intraionic electric-dipole transitions between the 4${\mathit{f}}^{\mathit{n}}$ and 4${\mathit{f}}^{\mathit{n}\mathrm{-}1}$5d configurations of rare-earth ions. The Faraday rotation and susceptibility of these compounds depend greatly on the splitting of the ground multiplet of the rare-earth ions in crystal fields. For non-Kramers ${\mathrm{Pr}}^{3+}$ ions in ${\mathrm{PrF}}_3$, the lowest crystal-field state is a singlet, so at very low temperature the behavior of the Verdet constant and susceptibility of ${\mathrm{PrF}}_3$ is different from ${\mathrm{CeF}}_3$ and ${\mathrm{NdF}}_3$. For ${\mathrm{CeF}}_3$, the mixed-valent behavior of Ce ions must be taken into account.

• Received 14 April 1992

DOI:https://doi.org/10.1103/PhysRevB.46.11636