MAGNETORESISTANCE IN NANOSTRUCTURED CO-AG PREPARED BY MECHANICAL-ALLOYING

Fine cobalt and silver powders have been ball-milled to yield a granul ar solid of composition Co30Ag70 in the form of coarse powder. The mat erial is an intimate mixture of grains of fcc Co in a silver matrix. T he cobalt is in the single-domain size range, and the samples exhibit coercivity (0.07 T at 296 K) and unusual thermomagnetic effects, inclu ding field-induced unidirectional anisotropy. There is a large, isotro pic negative magnetoresistance, which exceeds 10 % at 4.2 K.