Spin-dependent transport in hard superparamagnetic C:Ni nanocomposites

Structural, magnetic, and magneto-transport properties in C:Ni (30 at.%) nanocomposite films grown by ion beam cosputtering at 500 °C are investigated by means of transmission electron microscopy, superconducting quantum interference device magnetometry and electrical transport measurements. The C:Ni film shows a superparamagnetic behavior with a large coercivity field of 250 Oe at 5 K compared with bulk Ni metals. Anomalous Hall effect is observed in C:Ni nanocomposites, which is attributed to the scattering of spin-polarized carriers by the magnetic Ni nanoparticles in the carbon matrix.