PHASE AND PARTICLE-SIZE DISTRIBUTION IN MAGNETORESISTIVE FE-CU GRANULAR ALLOYS INVESTIGATED BY MOSSBAUER-SPECTROSCOPY

The size distribution of ferromagnetic particles in granular Fe-Cu all oys is derived from the hyperfine field distribution of Fe-57 Mossbaue r spectra, on the grounds of collective magnetic excitations associate d with the spectral line broadening. A good agreement with the X-ray d iffraction results is found for the average particle size estimated fr om the Mossbauer data. The magnetoresistance of a splat-cooled Fe25Cu7 5 alloy reaches a maximum of 3% after appropriate annealing and its ev olution is correlated with the various Fe phases (ferro, para and supe rparamagnetic) and particle sizes identified by the Mossbauer data.