Structural and magnetoresistive properties of mechanically alloyed Fe-Co-Ag

The structural, magnetic and magnetoresistive properties of a wide range of mechanically alloyed Fe-Co-Ag granular materials were investigated by means of x-ray diffraction, Mossbauer spectroscopy, differential scanning calorimetry, DC magnetometry and magnetoresistance measurements. Binary Fe-Co alloys, milled using Syalon containers, showed a mixed fcc-bcc structure for Fe compositions between 20 and 25 at.%. The ternary alloys were found to comprise dispersions of Fe-Co grains in an fee silver matrix, with the structure and magnetic properties of the Fe-Co grains mirroring those of the corresponding binary Fe-Co alloys. For materials with Fe-Co ratios in the region of the mixed fcc-bcc phases, additional components were noted in their Mossbauer spectra (a secondary sextet and a paramagnetic doubler, accounting for up to 63% of the spectral area), indicating the intermixing of a significant number of small Fe-Co clusters or fine grains into the Ag matrix. Alloys in this region were also found to have the largest magnetoresistive responses, with the maximum being a 5.8% effect in (Fe(0.15)Co(0.85))(30)Ag(70), as measured at 10 K in a field of 3 T. This indicates the dominant significance of fine grain intermixing in these alloys.