Creation of bulk, superlatticelike structure and giant magnetoresistance effect in a deformed Cu-Ni-Fe alloy

A spinodally decomposed Cu-20 Ni-20 Fe alloy containing ∼500 Å size ferromagnetic particles was uniaxially deformed to create a locally multilayered, superlatticelike structure with alternating ferromagnetic and nonmagnetic layers. When the size scale of each layer was made to be small, ∼15 Å thick, a dramatic improvement in room-temperature magnetoresistance ratio from ∼0.6 to ∼5% was obtained. An abnormal temperature dependence of magnetoresistance ratio, i.e., the room-temperature value being greater than that at 4.2 K, was found. The observed giant magnetoresistance behavior could be explained in terms of the field-induced decrease in electron scattering in a nearly superparamagnetic material although the spin-dependent scattering at the two-phase interface and in the ferromagnetic phase may also be a contributing factor.