Investigations on structural, optical and ferromagnetic properties of Ni doped ZnO nanotwins

Abstract

Ni doped ZnO nanotwin rods (nanotwins) have been fabricated by hydrothermal technique. Incorporation of Ni to the ZnO host lattice induces the morphological amendment which are being optimized and are investigated through scanning electron microscope. The diverse nature of interplanar spacing and orientation at the interface of ZnO nanotwins have been investigated through transmission electron microscope. Further, the local structure of Ni in the ZnO matrix has been studied through X-ray diffraction and X-ray photoelectron spectral analysis. Here, texture coefficient of (200) and photoluminescence spectra have been considered for the determination of defect states and the grain boundary mismatch. The existence of room temperature ferromagnetic property of the ZnO nanotwins has been manifested using magnetization hysteresis behavior. The optimized Ni ion concentration of 5% in ZnO nanorods yields nanotwins forming stable defects at Zn interstitial, oxygen vacancy and oxygen antisite helps to promote the ferromagnetic interaction to accomplish higher magnetic moment. Also, the presence of uncompensated surface spins in terms of charges on the surface of the nanoparticles have been analyzed through chronocoulometric analysis. The measured magnetic moment is 132 memu/g which is about 12 times greater than that of the pristine ZnO. In addition, the existence of room temperature ferromagnetism in ZnO nanotwins has been explained through bound magnetic polaron mechanism.