1 research outputs found
Search for Origin of Room Temperature Ferromagnetism Properties in Ni-Doped ZnO Nanostructure
The
origin of room temperature (RT) ferromagnetism (FM) in Zn<sub>1โ<i>x</i></sub>Ni<sub><i>x</i></sub>O (0< <i>x</i> < 0.125) samples are systematically investigated through physical,
optical, and magnetic properties of nanostructure, prepared by simple
low-temperature wet chemical method. Reitveld refinement of X-ray
diffraction pattern displays an increase in lattice parameters with
strain relaxation and contraction in Zn/O occupancy ratio by means
of Ni-doping. Similarly, scanning electron microscope demonstrates
modification in the morphology from nanorods to nanoflakes with Ni
doping, suggests incorporation of Ni ions in ZnO. More interestingly,
XANES (X-ray absorption near edge spectroscopy) measurements confirm
that Ni is being incorporated in ZnO as Ni<sup>2+</sup>. EXAFS (extended
X-ray absorption fine structure) analysis reveals that structural
disorders near the Zn sites in the ZnO samples upsurges with increasing
Ni concentration. Raman spectroscopy exhibits additional defect driven
vibrational mode (at 275 cm<sup>โ1</sup>), appeared only in
Ni-doped samples and the shift with broadening in 580 cm<sup>โ1</sup> peak, which manifests the presence of the oxygen vacancy (V<sub>O</sub>) related defects. Moreover, in photoluminescence (PL) spectra,
we have observed a peak at 524 nm, indicating the presence of singly
ionized V<sub>O</sub><sup>+</sup>, which may be activating bound magnetic
polarons (BMPs) in dilute magnetic semiconductors (DMSs). Magnetization
measurements indicate weak ferromagnetism at RT, which rises with
increasing Ni concentration. It is therefore proposed that the effect
of the Ni ions as well as the inherent exchange interactions arising
from V<sub>O</sub><sup>+</sup> assist to produce BMPs, which are accountable
for the RT-FM in Zn<sub>1โ<i>x</i></sub>Ni<sub><i>x</i></sub>O (0< <i>x</i> < 0.125) system