Magnetic and Mossbauer study of multiphase Fe-Zr amorphous powders obtained by high energy ball milling

The amorphous system Fe-Zr has been extensively studied due to its particular magnetic behaviour, especially in the concentration range around 90 at.% Fe, only accessible by rapid quenching. We have extended the study to lower Fe content alloys, by using mechanical alloying to synthesize FexZr100-x amorphous powders with x = 65, 70, 75. Mossbauer spectra and magnetization measurements have been performed as a function of temperature. Different magnetic measurements were performed to characterize the Curie temperatures of these multiphase samples and hyperfine field (B-hf) distributions, P(B-hf), were used to fit Mossbauer spectra below the Curie temperature (T-C) and quadrupole splitting distributions, P(Delta), above T-C, in agreement with the amorphous structures. The hyperfine field distributions of as-milled samples are characterized by two maxima and are fitted with two Gaussian curves that evolve with temperature in position, intensity and width. This bimodal behaviour has been also found in higher Fe content FeZr alloys as well as in ternary alloys with boron, and with nickel, and can be interpreted as arising from different neighbourhood Fe sites. The rather uncommon P(Delta) are also interpreted in the same terms.