Modulation-induced giant magnetoresistance in a spinodally decomposed Cu-Ni-Fe alloy

Giant magnetoresistance in a spinodally decomposed, bulk 60 Cu-20 Ni-20 Fe alloy is reported. An annealed, quenched, and heat-treated sample with a compositional modulation of ≲50 Å size exhibits a ΔR/R value as high as 9% at 4.2 K. Optimization of the ferromagnetic phase particle geometry through a combination of spinodal decomposition and uniaxial deformation led to a locally multilayered, superlattice-like structure and a dramatic increase in room-temperature magnetoresistance from ∼0.6 to ∼5%. This improvement in magnetoresistance is accompanied by a decrease in coercivity from ∼620 Oe in the fully decomposed material to ∼45 Oe in the optimized structure. Interestingly, this structure no longer exhibits the commonly observed temperature-dependent behavior of ΔR/R increasing at low temperatures, but rather shows a decrease at 4.2 K.