Magnetoresistance in a spinodally decomposed Cu-Ni-Fe alloy consisting of two ferromagnetic phases

We report a giant-magnetoresistance (GMR) phenomenon in a bulk, spinodally decomposed Cu-20Ni-20Fe alloy containing a 30 size, coherent compositional modulation. A negative and isotropic magnetoresistance value at 4.2 K as high as 9% has been obtained. It is interesting to note that the magnetoresistance effect varies drastically with temperature (by as much as ∼800% between room temperature and 4.2 K) while the M-H behavior changes very little in the same temperature range. As there was no noticeable dependence of magnetoresistance on the field orientation, anisotropic magnetoresistance effect is ruled out as the main cause. The nature of the observed phenomenon may be similar to that of the GMR effect typically seen in superlattice or granular films; however, this GMR effect is seen in a non-single-domain structure where both the particles and the matrix are ferromagnetic. © 1994 The American Physical Society.