1 research outputs found
Local Structure Investigation of Cobalt and Manganese Doped ZnO Nanocrystals and Its Correlation with Magnetic Properties
Co and Mn doped ZnO nanocrystals
have been synthesized by two different
routes, viz., a wet chemical method and a microwave-assisted nonaqueous
method and it has been found that the samples prepared by the former
method are ferromagnetic while those prepared through the later route
are paramagnetic. Systematic investigation of these doped ZnO nanocrystals
has been carried out by extended X-ray absorption fine structure technique
to determine the changes in the local structure at the Zn and dopant
sites. Co doped samples prepared by either of the techniques show
almost similar behavior, with Co substituting Zn up to a 10% doping
concentration, beyond which there is a signature of Co clustering.
However, in the case of Mn doped samples, Mn clustering commences
at lower values of doping (∼7%) for samples prepared by microwave-assisted
method, while for nanocrystals prepared by the wet chemical method,
Mn–K edge X-ray absorption near edge spectroscopy measurement
reveals the presence of a Mn<sub>2</sub>O<sub>3</sub> phase at lower
concentration and clustering at higher concentration (>10%). These
findings were supported by the results of optical and magnetic measurements
on the samples. The experimental results have been further corroborated
by first principle calculations. The findings suggest that the origin
of ferromagnetic properties in Co doped ZnO nanoparticles prepared
by the wet chemical method may be a consequence of surface modification
related to the preparation process and not related to bulk properties.
The ferromagnetism in Mn doped samples prepared by the wet chemical
method can be explained by the presence of a secondary Mn<sub>2</sub>O<sub>3</sub> phase. The Mn doped samples prepared by the microwave-assisted
method, on the other hand, manifest paramagnetism with a signature
of antiferromagnetic interaction due to Mn clustering at relatively
lower Mn concentration