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We have investigated the structural and magnetic properties of polycrystalline Cu‐substituted cobalt ferrite (CuxCo1−xFe2O4: x = 0.00, 0.15, 0.30, 0.45, 0.60) nanoparticles, synthesized via chemical coprecipitation method. The prepared samples were of single phase as confirmed by X‐ray diffraction analysis. The mean crystallite size ranged from 44 to 65 nm was obtained using Scherrer's formula. M‐T curves revealed that the Curie temperature of all the samples was above room temperature and it was found to decrease with increasing Cu concentration, which was supported by Mössbauer spectra. Field cooled (FC) hysteresis curves showed ferrimagnetic nature at 5 K and room temperature. It was observed that careful variation of Cu concentration in cobalt ferrite lead to weak A‐B interaction with tunable magnetic properties. [ABSTRACT FROM AUTHOR]

In this report, we studied various structural and optical properties of pure and copper-doped cadmium oxide (CdO) thin films. Nanostructured Cu-doped CdO films were deposited using sol-gel spin-coating technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) studies. The optical and electrical properties of the pure and Cu-doped CdO thin films were studied by UV-vis spectroscopy and four-point probe method, respectively. The XRD peaks show the formation of nanocrystalline CdO with cubic face-centered crystal structure. The band gaps of the as deposited films were found in the range of 2.32-2.73 eV, while after doping, it decreases due to structural deformation. The electrical resitivity was found to decrease approximately ∼10 in Cu-doped CdO thin films. [ABSTRACT FROM AUTHOR]

Phase-pure rutile SnO nanoparticles doped with various pairs of transition metals such as Fe-Ni, Fe-Mn, Ni-Mn, and Co-Mn have been synthesized using a sol-gel method. Average crystallite size of 22 nm to 29 nm with no impurity secondary phase was observed by x-ray diffraction (XRD) analysis. The morphologies of the particles were studied and their sizes calculated by field-emission scanning electron microscopy (FESEM). Emission at 338 nm in photoluminescence (PL) spectroscopy was observed and attributed to band-edge emission, while the peak at 470 nm was ascribed to doubly ionized oxygen vacancies. Raman spectroscopy confirmed the phase purity of the sample. The effects of oxygen vacancies broaden the E mode of the Raman spectrum. In Sn Mössbauer spectra, broadened line width was observed and the singlet was attributed to Sn valence state. The interaction between singly ionized oxygen vacancies and 3 d dopant ion is the reason behind the ferromagnetic ordering observed in magnetic studies. Spins pinned at the surface orient randomly, which decreases the total moment. [ABSTRACT FROM AUTHOR]

Adsorption of 3-aminopropyltriethoxysilane (APTS) on magnetite nanoparticles during its formation has been investigated to optimise the preparation of stable aqueous dispersion of amine derivatised magnetite nanoparticles. APTS adsorbs chemically on the surface of magnetite particle modifying its surface which is evident from thermal and C, H, N analysis. The variation of particle size has been observed with change of APTS concentration. X-ray diffractogram shows the formation of pure inverse spinel phase magnetite with average crystallite size 7 nm when equimolar (Fe3O4: APTS = 1:1) quantity of APTS was used during its synthesis. The presence of free surface –NH2 groups and Fe–O–Si bonds was observed by FTIR. Raman spectrum further confirms the presence of surface –NH2 groups. Transmission electron microscopy shows formation of particles of average size between 7 nm and 12 nm. The effective hydrodynamic diameter of the APTS coated particle agglomerates is 45.8 nm in stable aqueous colloidal dispersion, which is evident from photon correlation spectroscopy. VSM measurements at room temperature of both silanised and unsilanised magnetite shows their superparamagnetic nature with saturation magnetisation 41 e.m.u/g and 56 e.m.u/g, respectively. Avidin has been immobilised on the surface through glutaraldehyde, which demonstrates the possibility of the synthesised material to be used in protein immobilisation to form bioactive magnetic particles. [ABSTRACT FROM AUTHOR]

We report the microstructural and magnetic characterization of single phase nanocrystalline partially inverted Zn 0.3 Ni 0.7 Fe 2 O 4 mixed spinel ferrite. The samples were annealed at 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. X-ray diffraction results indicate phase purity of all the samples and application of Debye- Scherrer yielded a crystallite size variation from 5 nm to 33 nm for the different samples. Magnetic measurements have revealed the freezing of interfacial spins which were the cause of the large horizontal M-H loop shift causing large exchange bias with high anisotropy. The magnetic measurements show a hysteresis loop with high effective anisotropy constant due to highly magnetically disordered surface spin at 5 K. [ABSTRACT FROM AUTHOR]

Transition-metal-doped SnO 2 quantum dots were synthesized by chemical co-precipitation technique and investigated experimentally. The dots have the chemical composition Sn 1-x T x O 2 , where T = Cr, Mn, Fe, Co, and Ni (x = 0.02 and 0.04), and were capped by polyvinylpyrrolidone. X-ray diffraction analysis has confirmed an impurity-phase-free rutile structure of the samples and the size of the synthesized particles is of the order of 2.5 nm which is supported by the transmission electron micrograph. The fluorescence spectra of the samples confirm a strong blue shift in the near band edge (excitonic) emission peak. We also found emissions from surface localized excitons, tin atoms related defects and oxygen vacancies. The room-temperature M - H loops of the samples does not saturate in magnetic fields of up to 5 T. The magnetic data of the samples were explained on the basis of spin-flop transitions in uncompensated anti-ferromagnets. • Synthesis of transition-metal doped SnO 2 quantum dots. • Evidence of strong blue shift in the fluorescence spectra. • Magnetism mediated by spin-flop transitions. [ABSTRACT FROM AUTHOR]

In this paper we report the synthesis of Cr doped nickel ferrite denoted by the generic formula Ni 1− x Cr x Fe 2 O 4 ( x =0.05, 0.10 and 0.15) through a standard chemical co-precipitation method. An effort has been made to study the effect of doping of trivalent ions on the formation of cationic vacancies in the crystal. The structural characterization of the samples was carried out using X-ray diffraction and Raman spectroscopy. X-ray diffraction confirmed the formation of single spinel phase. The refinement of the pattern using GSAS showed the presence of cationic vacancies in all the three samples which give rise to compressive strain. Raman spectroscopy and Mössbauer measurements indicated distortion in the crystal structure as doping of Cr 3+ was increased. The magnetic measurements of all the samples exhibited negligible coercivity coupled with ferrimagnetic nature indicating very low magnetic anisotropy. Additionally the samples showed a steep magnetization curve making it an attractive choice for magnetic switching applications. [ABSTRACT FROM AUTHOR]