Point defect-induced magnetic properties in CuAlO₂ films without magnetic impurities

The magnetic properties of the undoped CuAlO₂ thin films with different compositions are examined. In order to understand this phenomenon and to determine the correlation between the magnetic and electrical properties and point defects, the X-ray photoelectron spectroscopy and Hall effect measurements are performed. Combining with Hall effect, X-ray photoelectron spectroscopy and alternating gradient magnetometer measurements, a direct link between the hole concentration, magnetism, copper vacancy (V_Cu), oxygen vacancy, and interstitial oxygen (O_i) is established. It is shown that an increase in the number of acceptors (V_Cu and O_i) leads to an increase in the hole concentration. Based on theoretical and experimental investigations, the authors confirmed that both acceptors (V_Cu and O_i) in CuAlO₂ could induce the ferromagnetic behavior at room temperature.