Magnetic phase tuning of diluted Fe-doped CuO nanoparticles through annealing temperature as characterized by first-order reversal curve analysis

摘要

Diluted magnetic semiconductors (DMSs) exhibit room temperature ferromagnetic behavior and have recently been used in a broad range of applications including spintronic devices. Here, we present a simple co-precipitation method to synthesize pure CuO and diluted Cu1-xFexO (x = 0.05 and 0.1) nanoparticles (NPs) with different annealing temperatures (T-a) ranging between 500 degrees C and 900 degrees C, achieving ferromagnetic DMSs with a monoclinic structure at room temperature. The mean NP size, evaluated using a field-emission scanning electron microscope, was found to increase with increasing T-a. A red shift was observed in UV-visible spectra and indicated the successful substitution of Fe ions in the CuO NPs, confirming the absence of impurity phases in the resulting structures. Investigating magnetic properties by hysteresis loop measurements, maximum saturation magnetization and coercive field values were obtained to be 4.8 emu/g and 325 Oe, respectively, for 10% Fe-doped CuO NPs at T-a = 900 degrees C. First-order reversal curve analysis was used to study detailed magnetic characteristics of the NPs. While a soft magnetic phase with superparamagnetic fractions ranging from approximately 41% to 53% dominated magnetic behavior at T-a = 700 degrees C, a strong hard phase determined the average magnetic properties of Fe-doped CuO NPs with nanocrystalline structure at T-a = 900 degrees C.