Pulsed electrodeposition of nanocrystalline Cu–Ni alloy films and evaluation of their characteristic properties

Abstract

The preparation of nanocrystalline Cu–Ni alloy films by pulsed electrodeposition process and their structural, morphology, thermal characteristics and magnetic properties are addressed. The study reveals that the film composition, lattice constant and magnetic properties of the films could be controlled by the applied current density and duty cycle. Energy dispersive X-ray analysis (EDX) confirms that the Cu–Ni alloy film has a stoichiometry of Cu0.98Ni0.02, Cu0.95Ni0.05, Cu0.89Ni0.11, Cu0.77Ni0.23, Cu0.56Ni0.44 and Cu0.38Ni0.62 that are obtained at 2.5, 5, 7.5, 10, 15 and 20 A/dm2, respectively. The X-ray diffraction (XRD) measurements confirm that all the six Cu–Ni alloy films of the present study possess the f.c.c. structure. The lattice constant is found to decrease with increase in nickel content of the Cu–Ni alloy. The crystallite size lies in the range of 15 to 46 nm for as-plated alloys and increases from 20 to 114 nm, following vacuum annealing at 400 °C for 1 h. The differential scanning calorimetry (DSC) trace indicates a broad exothermic peak characteristic of nanocrystalline materials. The vibrating sample magnetometer (VSM) study reveals that, among the six types of Cu–Ni alloy films, the films obtained at 2.5 and 5.0 A/dm2 are diamagnetic; the one obtained at 7.5 A/dm2 is weakly ferromagnetic, whereas those obtained at 10, 15 and 20 A/dm2 are ferromagnetic. The saturation magnetization increases with increase in nickel content of the Cu–Ni alloy film.