Structural, optical and magnetic properties of CuO/α-Fe₂O₃ nanocomposites: effect of Fe concentration and annealing temperature

The impact of annealing temperature (500, 600, and 700 °C) and Fe concentration on the formation of 5, 10 and 20 at.% Fe-doped CuO was investigated using structural, optical, and magnetic characterizations. XRD and Raman studies confirmed the presence of both CuO and α-Fe₂O₃ in the composite samples. The broadening of the multiphoton transition mode in the Raman spectra with increasing Fe concentration and annealing temperature could be associated with the defects. FESEM analysis showed that the sample's morphology changed from non-homogeneous, irregularly shaped flake-like particles to nearly spherical particles with increased Fe concentration. Optical characterization suggested that the samples' higher optical band gap energy (> 3 eV) could result from the quantum confinement effect. Photoluminescence analysis revealed that the rise of annealing temperature from 500 to 600 °C led to a shift in the emission coordinates from the near-green to the blue region. All the samples showed a clear hysteresis loop at room temperature indicating the ferromagnetic nature. The maximum coercivity of 777 Oe and highest remanent magnetization of 2.06 emu/g was found for the 20% Fe-doped CuO annealed at 700 °C. On the other hand, the 5% Fe-doped CuO samples exhibited an exchange bias field of ~ 31 Oe at 300 K.