Room-temperature structural, magnetic, and dielectric characteristics of La-doped CuO bulk multiferroic

In this manuscript, we report room-temperature structural, microstructural, optical, dielectric, and magnetic properties of CuO and Cu0.995La0.005O ceramics, synthesized by solid-state reaction method. La doping in CuO leads to the evolution of compact and dense microstructure with reduced porosity. Due to noticeable differences in the ionic radii of Cu2+ (0.73 Ǻ) and La3+ (1.03 Ǻ), La doping creates vacancy defects which induces considerable strain in the CuO lattice resulting in a reduction in the lattice parameters and cell volume. However, both ceramics process similar monoclinic structure with C2/c space group. Detailed characterization using X-ray photoelectron spectroscopy, Raman, and Fourier-transform infrared spectroscopy confirmed the incorporation of the La3+ in CuO lattice. Interestingly, La doping enhances the dielectric constant and results in a reduced leakage current. The onset of large dielectric constant is attributed to dense microstructure and strain/distortion in CuO lattice after La doping. Additionally, the bandgap of Cu0.995La0.005O ceramics decreases which is attributed to increased vacancy defect concentration that creates intermediate dopant energy level within bandgap of CuO matrix. Furthermore, improvement in magnetic and dielectric properties is also discussed and correlated with the grain size in La-doped CuO.