Granular Nix (SiO2)100−x thin films as low temperature thermometers

Abstract
A series of granular Nix (SiO2)100−x thin films have been prepared by rf sputtering with nickel concentrations between 60 and 90 at. %. The temperature dependence of the resistance is strongly composition dependent. In films with Ni concentrations below 70%, the resistance increases as the temperature decreases, but shows a crossover to a weaker temperature dependence below about 1 K. The magnetoresistance of these materials is small and negative in applied magnetic fields up to 6 T. The temperature dependence of the resistance and the small magnetoresistance indicate that films with Ni concentrations near 66% may be useful for thermometry over a wide range of temperatures.