Ni–TiO2 nanocomposite films and their magnetic properties

Abstract

We have demonstrated a method for preparing nickel nanoparticles in TiO2 matrix films, 500–900nm thick, using magnetron sputtering followed by a heat treatment at temperatures 723–773K for 1h in various gas atmospheres. The X-ray diffraction indicated that the size of Ni crystallites was 4–6nm depending on the heat treatment conditions. Magnetic force and scanning electron microscopy studies show clustering the nanoparticles to size of order hundreds of nm arranged in a shape of nanopillars separated by TiO2. The above mentioned clustering results in a magnetic anisotropy as indicated from the loops of the magnetic moment – magnetic field curves in the perpendicular and parallel directions. Some of the prepared nanocomposite samples exhibit different magnetic behavior within the perpendicular and parallel directions for |μ0H|>0.6T, presumably due to the presence of antiferromagnetic oxides.