Giant magnetoresistance inCr100−xFexbulk granular alloys

We report on the observation of giant magnetoresistance in magnetically inhomogeneous bulk granular ${\mathrm{Cr}}_{100\mathrm{-}\mathit{x}}$ ${\mathrm{Fe}}_{\mathit{x}}$ alloys. The largest magnetoresistance among the investigated alloys of 10.7≤x≤49.0 at. % amounts to 26% for x=18.9 at. % at 5 K and 4 T. This is substantially larger than in other bulk random 3d alloys and is of the same order of magnitude as that in granular films. Concentration, temperature, and field dependences of the magnetoresistance are also similar to those observed in granular media. The origin of giant magnetoresistance in bulk Cr-Fe is attributed to the field-induced alignment of Fe-rich ferromagnetic clusters in a Cr-rich matrix. Giant magnetoresistance in Fe-Cr collapses just above x=20 at. %, at which long-range ferromagnetic order sets in.