Giant magnetoresistance in electro-deposited Co-Cu granular film

CoxCu100-x granular films have been successfully prepared by electrodeposition. The influences of deposition parameters and post-deposition annealing condition on giant magnetoresistance (GMR) have been studied in detail, using transmission electron microscopy (TEM), vibrating sample magnetometer and resistance measurements. It is found that, as for other methods, post-deposition annealing is crucial for obtaining larger GMR value. Under the optimum annealing condition, namely, annealing one hour at 695 K, GMR reaches a maximum value of -5% at room temperature, 1.3 T and -10% at 77 K, 0.9 T. A detailed TEM investigation shows that the grain size distribution follows a log-nonnal function. Using a recently developed model that takes explicitly into account the magnetic moment distribution (therefore grain size distribution) and spin-dependent electron-impurity scattering within magnetic grains and at the interface between grains and matrix for the granular films with superparamagnetic particles and considering the contribution from ferromagnetic grains, both experimental M-H and GMR-H curves have been well fitted with this log-normal size distribution. Our results confirm this model and evidence that the spin-dependent scattering at the interface between magnetic grains and non-magnetic matrix plays a dominant role for GMR, and grain size distribution is crucial in explaining the experiment results on GMR.