Current Applied Physics, Vol.16, No.2, 175-182, 2016
Defects due to lattice distortion and nano-size intermediate ferromagnetism in La, Gd substituted Zn0.95Co0.05O
We have reported the long-range ferromagnetic interactions in La and Gd doped Zn0.95Co0.05O (ZCO5) [Zn0.92Co0.05La0.03O (ZCLO53) and Zn0.92Co0.05Gd0.03O (ZCGO53)] nanostructures due to defects that formed by lattice deformation and vacancies. These nanostructures were prepared by sol-gel method. X-ray diffraction shows hexagonal Wurtzite ZnO and the lattice parameters are highly influenced by doping. TEM analysis depicted nano-aggregation type product. FTIR spectra have shown organic contribution and metal-oxygen vibrational band in the samples. The Wurtzite structure with La and Gd doping in ZCO5 is also confirmed by Raman modes with introducing lattice defects, vacancies and interstitials formation. Both the band gap energy and defects related vacancies performed PL emission. The long-range ferromagnetic order occurs due to strong antiferromagnetic interactions that performed by La and Gd doping in ZCO5. It results into antiferromagnetic 3d, 4f-3d, 4f-5d-4f transitions. The zero-field and field cooling at H = 500 Oe in the temperature region, T = 300-5 K is used to evaluate the blocking temperature of phase transition. Here, the medium for long-range ferromagnetic interactions is defect carriers. The bound magnetic polaron model has been described the resulting magnetic behavior. The chemical valance states of La3+ and Gd3+ induce superexchange magnetic interaction due to F-center mechanism. (C) 2015 Elsevier B.V. All rights reserved.