Effect of heat-treatment on magnetic properties of non-graphitic disordered carbon

Heat-treatment effect on the electronic properties is investigated by magnetic susceptibility and ESR measurements in relation to structural change for non-graphitic but sp 2-rich disordered carbon thin-film prepared by pulsed laser deposition. X-ray diffraction reveals that the sp 2/sp 3-jumbling ‘non-graphitic’ structure of non-heat-treated sample with atomic-scale disorder is easily relaxed into the nano-sized ‘graphitic’ island-network by heat-treatment at approximately 600 °C, preserving the sp 2/sp 3 ratio in the sample at ∼90%. According to the temperature dependence of magnetic susceptibility, non-heat-treated sample shows the Curie–Weiss behavior with the large Pauli paramagnetic temperature-independent term and antiferromagnetic interaction whose strength is significantly larger than that simply expected from the average spin–spin distance. The temperature dependence of ESR signal intensity confirms the large contribution of the Pauli paramagnetism in the non-heat-treated sample.