Crystal Field Effects in Rare Earth Compounds

Abstract

We review the effect of the crystal field on thermal properties in intermetallic rare earth compounds. In substances where single ion effects are predominant, we give experimental results for the specific heat, thermal expansion, magnetic susceptibility and elastic constants. All these thermodynamic derivatives show clear cut crystal field effects (TmSb). Coupling constants deduced from these measurements are discussed. In substances, where the ions are interacting, we concentrate on elastic constants. We show how quadrupole‐quadrupole coupling constants g′ can be determined from the temperature dependence of certain symmetry elastic constants (rare earth pnictides, TmCd, TmZn, PrCu2). We argue that g′ is in large part due to conduction electron aspherical Coulomb charge scattering. A valence fluctuation system (TmSe) will be mentioned. Finally magnetic field effects on elastic constants will be given, with particular emphasis on rotational strain effects.