Effect of doping on the structural, magnetic, and ferroelectric properties of Ni1-xAxTiO3 (A = Mn, Fe, Co, Cu, Zn; x = 0, 0.05, and 0.1)

In order to create a new NiTiO₃-based system of ferromagnetic material at room temperature, powdered ABO₃ ilmenite structure titanates with the composition Ni_1-xA_xTiO₃, where A = Mn, Fe, Co, Cu, and Zn, and x = 0, 0.05, and 0.1, were synthesized using the sol-gel method. X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy (RAMAN), Fourier-transform infrared spectroscopy (FT-IR), vibrating-sample magnetometer (VSM), and TF-2000 analysis methods were employed to systematically investigate the crystal sizes, morphologies, structural, magnetic, and ferroelectric properties of the samples. Fe- (x = 0.1), Cu- (x = 0.05), and Zn- (x = 0.05) doped NiTiO₃ samples displayed ferromagnetic properties at room temperature. The polarization-electric field curves confirmed the ferroelectric properties of these samples, which were present at room temperature. These ferroelectric properties were lower than in the undoped NiTiO₃ samples, and the ferromagnetic properties in the samples had different origins. The ferromagnetism in Fe- (x = 0.1) doped sample was attributed to spin splitting of transition metal and oxygen vacancies, while, oxygen octahedra distortion caused by Ni site substitution was responsible for the ferromagnetism in Cu- (x = 0.05), Zn- (x = 0.05) doped samples. This is because the ferromagnetic phase with non-uniform domain structure, when mixed into the ferroelectric phase in the presence of applied electric field acts as pores, and breaks the electric circuit, resulting in a decrease in ferroelectric parameters.