Giant magnetoresistance in Co-Cu granular alloy films and nanowires prepared by pulsed-electrodeposition

摘要

Granular Co sub(x)Cu sub(1-) alloy films and nanowires were prepared by pulsed-electrodeposition. The alloy composition was changed by controlling pulse-width of the current pulse with fixed off-time of the deposition. Alloy films were formed onto evaporated Cu films grown on glass plates. The face-centered cubic lattice parameter was found to decrease with increasing Co content in the films in the composition range investigated (0.17 less than or equal to x less than or equal to 0.66), and the second phase, probably by hexagonal close-packed phase, appeared at x greater than or equal to 0.42. The crystallite size of the as-deposited condition calculated using the XRD data and the Scherrer's formula ranged between 10-30 nm. The magnetoresistance (MR) was found to become larger after annealing at an appropriate temperature between 400-600 degree C. The maximum value of the MR ratio of about 4% was observed at the composition around x identical with 0.2. Magnetic hysteresis curves were measured for Co sub(0.31)Cu sub(0.69) and compared with those reported for sputtered alloy films. Granular nanowires prepared into the pores of the alumite plate were also examined and reported briefly.