Evolution of room temperature ferromagnetism with increasing 1D growth in Ni-doped ZnO nanostructures

Zn1-xNixO (x = 0, 0.03, and 0.5) 1D nanostructures showing room temperature ferromagnetism (RT FM) with high moment have been synthesized by a solvothermal route. X-ray diffraction, transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDS) and X-ray photoelectron spectroscopy (XPS) analysis reveal the growth of single phase wurtzite structure Zn1-xNixO NRs of diameter 60 -70 nm and length of 0.4-0.6 mm with the successful incorporation of Ni ions inside ZnO matrix. High resolution TEM lattice images show that all the NRs are single crystalline with a d-spacing of 2.57 angstrom with c-axis growth. Room temperature magnetic measurements exhibit strong ferromagnetic characteristic with magnetic moment of 1.13 emu/g, coercivity of 150 G. Photoluminescence (PL) spectra exhibit near band edge UV emission as well as defect related visible emission which is expected to play a significant role in the FM ordering, also PL spectra reveal slight band edge modification due to doping effect. Systemic structural, magnetic, and optical properties reveal that both the nature of the defects as well as Ni2+ ions are significant ingredients to attain FM characteristics with high moment and ordering temperature in the 1-dimensional ZnO NRs. Magnetic interaction is analysed using a bound magnetic polaron model and expected to arise from the intrinsic exchange interaction of Ni ions, Zn Vacancy and O iterstitial related defects. (C) 2015 Elsevier B.V. All rights reserved.