Ni-TiO2 nanocomposite films and their magnetic properties

We have demonstrated a method for preparing nickel nanoparticles in TiO2 matrix films, 500-900 nm thick, using magnetron sputtering followed by a heat treatment at temperatures 723-773 K for 1 h in various gas atmospheres. The X-ray diffraction indicated that the size of Ni crystallites was 4-6 nm 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|>0.6 T, presumably due to the presence of antiferromagnetic oxides.