Investigation into the Origin of Crystalline Electric Field Effects on Rare Earth Ions: I. Contribution from Neighbouring Induced Moments

Abstract

In order to determine how far it is possible to account theoretically for crystalline electric field parameters of rare earth ions a comparison is made between the experimentally determined parameters of Pr3+ in PrCl3 and PrBr3 and those calculated on a simple ionic model. As a point charge model is found to be inadequate, a general expression for the contribution of induced moments of any order on neighbouring ions to the crystalline electric potential at the rare earth site is given. This is used to evaluate the contribution of induced dipoles and induced quadrupoles to the crystalline electric potential at the Pr3+ site in PrCl3, and of induced dipoles to the crystalline electric potential at the Pr3+ site in PrBr3. Although the contribution of the induced moments to the potential is found to be significant, there are still some large discrepancies between calculated and experimental values. Possible reasons for these are discussed.