New ultrafine-flowers compositions based on Mn, Fe and Co multi-doped p-type NiO semiconductor: enhanced ferromagnetic and dielectric properties

In this study, Ni_0.97Mn_0.01Fe_0.01Co_0.01O composition exhibits a giant dielectric permittivity and strong ferromagnetic hysteresis loop at ambient temperature. Pure, (Mn, Co) codoped and (Mn, Fe, Co) tri-doped NiO powders were synthesized by sol–gel route. The crystal structure based on X-ray diffraction analysis verified that all samples have a cubic NiO phase with small crystallite sizes within 11–14 nm. The field emission scanning electron microscope (FESEM) image of pure NiO powder reveals the formation of particles have sheets shape. The FESEM micrographs of Ni_0.97Mn_0.015Co_0.015O and Ni_0.97Mn_0.01Fe_0.01Co_0.01O powders show a flower-like microstructure with homogenous size and distribution. The flower-like microstructure mostly made up of thin nanosheets particles. The band gap energy (E_g) of NiO, Ni_0.97Mn_0.015Co_0.015O and Ni_0.97Mn_0.01Fe_0.01Co_0.01O compositions was estimated to be 3.45, 3 and 2.9 eV, respectively. Both treated NiO compositions have long absorption impurity states until nearly 1.8 eV, indicating a high harvesting capacity for visible light spectrum. Ni_0.97Mn_0.015Co_0.015O and Ni_0.97Mn_0.01Fe_0.01Co_0.01O samples reveal giant dielectric permittivity with measured values of 6325 and 27,934 at 42 Hz, respectively. Magnetically, the tri-doping by (Mn, Fe, Co) blend noticeably advance the ferromagnetic performance and multiple the magnetic parameters of NiO with measured saturation magnetization, coercivity and remanence of 3.12 emu/g, 290 Oe and 0.58 emu/g, respectively. The obtained results indicated that the (Mn, Fe, Co) tri-doped NiO semiconductor is a highly promising system for capacitive charge energy storage and spin-electronics devices.