GD-155 MOSSBAUER-EFFECT AND MAGNETIC-PROPERTIES OF AL-SUBSTITUTED GD2FE17

We have investigated the effect of Al substitution on the magnetic properties and the Gd-155 Mossbauer spectra of Gd2Fe17-xAlx. Marked changes were observed in the values of the electric field gradient derived from the quadrupole splitting of the spectra, the effective Gd hyperfine field and the isomer shift. The implications of the sign reversal of the electric field gradient on the crystal field-induced magnetic anisotropy is discussed. The variation in the hyperfine field across the series has been attributed to a gradual reduction in the transferred hyperfine field, owing to the Fe moments. The variation in the isomer shift was shown to be in agreement with model predictions.