Magnetic behavior of sputtered Co-doped indium-tin oxide films

We have studied Co-doped indium-tin oxide (ITO) films deposited by magnetron sputtering on fused-quartz substrates under various conditions. We find that the magnetic and electrical transport properties of these films vary strongly with post-growth treatment. In films with more than 8 at. % of Co, we observe irreversible magnetization and an anomalous Hall effect that are likely caused by a mixed magnetic state, with metal-rich nanoclusters within a ITO:Co matrix. Homogeneous films with less than 8 at. % of Co are ferromagnetic at room temperature. Their magnetic behavior is consistent with a bound magnetic polaron percolation model.