Hydrothermal synthesis and magneto-optical properties of Ni-doped ZnO hexagonal columns

Single crystal Zn1-xNixO (x=0, 0.02, 0.04, 0.06) hexagonal columns have been synthesized by a simple hydrothermal route. The hexagonal columns of the products are about 3 mu m in diameter and about 2 mu m in thickness. X-ray diffraction (XRD), Ni K-edge XANES spectra and TEM indicate that the as-prepared samples are single-crystalline wurtzite structure and no metallic Ni or other secondary phases are found in the hexagonal columns. Optical absorption and Raman results further confirm the incorporation of Ni2+ ions in the ZnO lattice. Magnetic measurements indicate that the Zn1-xNixO hexagonal columns exhibited obvious ferromagnetic characteristic at room temperature. The coercive fields (H-c) were obtained to be 135.3, 327.79 and 12729 Oe for x=0.02, 0.04 and 0.06, respectively. The ferromagnetism was assumed to originate from the exchange interaction between free carriers (holes or electrons) from the valence band and the localized d spins on the Ni ions. (C) 2014 Elsevier B.V. All rights reserved.