Crystal field effects in the ESR of gadolinium in polycrystalline cubic metallic compounds

The electron spin resonance of gadolinium was measured on polycrystalline samples of the cubic metallic monopnictides of type MX (M = Sc, Y, La, Lu; X = P, As, Sb, Bi). For most of these systems the spectra show a characteristic line structure which clearly reflects the influence of the crystal field. The cubic crystal field parameter b4 of Gd is known from previous measurements on single crystals for YSb, YBi, LaSb and LaBi. In the present work the spectra of Gd are compared for LaSb powder samples and single crystals. This yields a method for deriving the crystal field parameter b4 from spectra of polycrystalline samples. In this way the values of b4 of Gd are determined for ScAs, YAs, LaP, LaAs, LuP and LuAs; for ScP and YP an upper limit can be given. The variation of b4 is discussed in terms of lattice parameter and covalency throughout this series of compounds. (author)