THEORY OF FARADAY-ROTATION AND SUSCEPTIBILITY OF RARE-EARTH TRIFLUORIDES

A theoretical investigation on the magneto-optical and magnetic properties of light rare-earth trifluorides CeF3, PrF3, and NdF3 is presented, The 0.6328-mum-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 4f(n) and 4f(n-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 Pr3+ ions in PrF3, the lowest crystal-field state is a singlet, so at very low temperature the behavior of the Verdet constant and susceptibility of PrF3 is different from CeF3 and NdF3. For CeF3, the mixed-valent behavior of Ce ions must be taken into account.