Resonance observations in cubic laves phase rare earth compounds

Abstract

N.M,R. Spin Echo spectra of Gd(_1-x)xYxAP(_2) and Gd(_1-x)La(_x)AP(_2) (0 ≤ x ≤ 0.4) were studied in the ferromagnetically ordered state at 4»2 K. The Al resonance line profiles were analysed under the assumption of various models for the spatial extent of the conduction electron polarization and general confirmation of RKKY like oscillatory polarization was found. Slowly decreasing nonoscillatory polarization functions were shown to be unable to explain the observed spectra. The line shape has been shown to depend rather critically on the value of the Ferml wave vector K(_f). The effect of the conduction electron mean free path on the line shape is similar to the E.S.R. of Gd in YAp(_2) was measured in the temperature range from 65 K to 340 K, The experimental results are discussed using Hasegawa's theory. The dependence of line width on temperature and Gd - concentration indicates the existence of a "bottleneck" in the relaxation between the conduction electrons and the lattice. The behaviour of the line width with temperature in the ferromagnetic region makes it possible to study the Curie temperature for these compounds. The hyperfine field at the S^Co nucleus have been observed for some of A Cog (A - rare earth metal) compounds. The field strength has essentially the same value of about 60 kOe|- for all the compounds studied. The results can be interpreted in terms of contributions to the hyperfine field arising from the transition metal sublattice and from the rare earth sublattice. The former appears to be proportional to the magnetic moment associated with the transition metal ion while the rare earth contribution is taken to arise predominantly from conduction electron polarization.