Structural, Optical, and Magnetic Properties of Nanocrystalline Co Doped SnO₂ Based Diluted Magnetic Semiconductors

Abstract

With the aim of understanding the structural, electronic, and magnetic properties of nanocrystalline Co doped SnO2 diluted magnetic semiconductors, prepared by the tartaric acid gel route, a systematic investigation as a function of annealing temperature has been carried out. The precursor was characterized by TG-DTA to determine thermal decomposition and crystallization temperature. The XRD, TEM, FT-IR, and laser Raman studies revealed that all the samples have a tetragonal rutile structure with single phase. The average particle sizes obtained from TEM are in the range of 18−50 nm. The changes in Raman spectra were analyzed with varying crystallite size. The optical absorbance measurements revealed that the nanometric size of the materials influences the energy band gap values. From the XPS studies, the oxidation state of cobalt is found to be +2, and particle size induced implications in the core level XPS peaks of Co 2p and O 1s have been analyzed. The presence of room temperature ferromagnetism has been confirmed by the magnetization studies. Finally, it has been concluded that the ferromagnetic properties depend not only on the surface diffusion of Co ions and the distribution of defects such as oxygen vacancies or vacancy clusters but also on nanometric size of the materials and their surface conditions.

An Elaborated Study of CO Sensitivities of Cu, Pt and Pd Activated SnO₂ Sensors: Effect of Precipitation Agents, Dopants and Doping Methods

“…The 6-unit cell atoms give a total of 18 branches for the vibrational modes in the first Brillouin zone. The mechanical representation of the normal vibration modes, all the vibrational modes of SnO2 with corresponding Raman shift peaks were also widely known and reported by various authors [42][43][44]. Table 3 resumes different frequencies of the optical modes of SnO2, with corresponding vibrational directions.…”

“…The rate of decrease in A1g peak intensity is higher for chemically doped powders than the impregnated ones. No peak shifts were observed from the Raman spectra, the minimum amount of doping percentage for observing a peak shift in Raman spectra was around 3 wt % [43][44][45]. Figure 3b shows a comparison of the Raman spectra of chemically doped Cu, Pt and Pd: SnO2 with urea as precipitation agent.…”

Synthesis of Hierarchical SnO₂ Microflowers Assembled by Nanosheets and Their Enhanced Photocatalytic Properties

“…In the nanocrystalline SnO 2 based system, as the surface properties are sensitive not only to the grain size and their distributions but also to the oxygen vacancies and local disorder, there may be a possibility of the appearance of new modes in the Raman spectrum. 20) The UV-vis absorption spectrum of SnO 2 microflowers is shown in Fig. 4.…”

Hydrothermal Synthesis of Gadolinium (Gd) Doped Cerium Oxide (CeO2) Nanoparticles: Characterization and Antibacterial Activity

“…In Gd doped CeO 2 NPs, the 2θ value of (111) plane is shifted towards lower side when the concentrations of Gd is increased. It happened due to the replacement of dopant ion in the CeO 2 lattice 18 . In addition, the peak broadening taken place in Gd doped CeO 2 nanoparticles as compared with that of pure CeO 2 synthesized without Gd.…”