Variations in the Magneto-optical Properties of CuAl_1-xFe_xO₂ with Fe Concentration

CuAlO₂ is among several ternary delafossites in which the electronic bandgap (2.68 eV) is less than the optical bandgap (3.5 eV). Because alloying is expected to allow band engineering in delafossites, we are investigating magneto-optical properties of CuAl_1-xFe_xO₂ for x = 0 to1. The samples were prepared by solid-state reaction in air. X-ray diffraction of the powder samples shows an expansion of the rhombohedral unit cell with increasing x, in accordance with Vegard’s Law. X-ray photoelectron spectroscopy, and SEM-based energy dispersive (x-ray) spectroscopy were also used to confirm the Fe concentrations. Analysis of the magnetization (M) vs. temperature data (T = 2 to 300 K) and magnetic field (up to H = 90 kOe) verifies Fe³⁺ as the electronic state of Fe and Fe³⁺-Fe³⁺ exchange coupling signifies anti-ferromagnetism for CuAl_1-xFe_xO₂ for x = 0 to 0.1. The high-resolution M vs. H hysteresis loop measurements done at 300 K and 10 K shows some hysteresis, particularly for the x= 0.1 sample. However, it is concluded that this hysteresis is due to hematite impurity which is not detectable in the XRD analysis of the samples. In this talk, we will specifically report on magnetic measurements of CuAl_1-xFe_xO₂ for x > 0.1 and optical absorption studies in the CuAl_1-xFe_xO₂ samples.