Magnetic properties of Fe-doped CuAlO2 and role of impurities

The delafossite CuAlO2 is a rare p-type semiconductor with potential applications as a thermoelectric and as a dilute magnetic semiconductor when doped with transition metal ions. Reported here are results from our investigations of CuAl1-xFexO2 (x = 0, 0.01, 0.05, and 0.1) with a focus on the x-dependence of structural and magnetic properties, and role of impurities. The samples prepared by the solid-state reaction at 1,100°C were characterized by X-ray diffraction (XRD), energy dispersive (X-ray) spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The magnetic results show that the Curie constant (C), low temperature magnetization (M) and the lattice constants scale with x. High resolution M-H loop measurements at 300 K and 10 K show negligible coercivity HC at 10 K but HC ∼ 100 Oe at 300K. These results suggest the presence of minute quantities of hematite (α-Fe2O3) that are not detected in our XRD and XPS. The role of impurities on the published results in this system is discussed.