A study of the lineshape of the NMR spin echo spectra of the compounds Gd_1-xY_xAl₂ and Gd_1-xLa_xAl₂

NMR spin echo spectra of Gd_1-xY_xAl₂ and Gd_1-xLa_xAl₂ (0<or=x<or=0.30) 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 a RKKY like oscillatory polarization was found. Slowly decreasing nonoscillatory polarization functions are shown to be unable to explain the observed spectra. The line shape is shown to depend rather critically on the value of the Fermi wavevector k_F. The polarization seems to decrease less strongly with distance than might be expected from the RKKY function.