Magnetoresistance of Cu–Ni nanoparticles in hydrogenated amorphous carbon thin films

Cu NPs in hydrogenated amorphous carbon (a-C:H) thin films without and with different thicknesses of Ni NPs layer were prepared by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition from acetylene gas and Cu and Ni targets. The content of thin films was characterized by Rutherford back scattering spectra and X-ray diffraction. The variation of the surface morphology with Ni NPs layer thickness was investigated by atomic force microscopy. The magnetoresistance (MR) of thin films without and with different thicknesses of Ni NPs layer was measured at room temperature and low magnetic field. A negative MR was observed for Cu NPs in a-C:H thin film that is changed to positive MR when Ni NPs layer thickness reaches to 10 nm and surface morphology is varied. The interesting plateaus are observed in MR that can be related to quantum confinement effect or collective movement of particles in the soft matrix of the a-C:H thin film.