Articles you may be interested inMicrostructure and magnetic properties of MFe2O4 (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method J. Appl. Phys. 117, 17A328 (2015) We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe 2 O 4 ) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20-27 GPa to 7.5-12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B 0 ¼ 204 GPa) is considerably larger than the value previously reported for bulk CoFe 2 O 4 (B 0 ¼ 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B 0 ¼ 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible. V C 2015 AIP Publishing LLC. [http://dx

The structural and magnetic properties of Fe (3−x) Zn x O 4 (x : 0, 0.1, 0.2, 0.5, 1) nanoparticles, prepared by wet chemical method, have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, and magnetization measurements. The nanoparticles are polyhedrical-shaped with a narrow distribution in size as it was verified by SEM. By Rietveld analysis of XRD patterns, it was determined that the crystallites' sizes of Fe (3−x) Zn x O 4 in spinel structure is in the range of 30 to 50 nm. Hysteresis cycles, measured at different temperatures (300, 200, 100, 50, and 7 K), showed an increase in saturation, while temperature is diminished, as it is expected. All the samples, exhibited a high blocking temperature of ∼350 K, as it was determined by ZFC-FC measurements. This fact, reveals their strongly interacting superparamagnetic nature. Real ac susceptibility increases with temperature, while the imaginary part has a maximum, which depends on frequency, and it is related to a critical temperature, which depends on composition. A Néel-Arrhenius dependence of frequency on the critical temperature was found for all the samples. We determined a minimum of the effective anisotropy for x = 0.2.

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Nanoparticles of V-doped SnO 2 with stoichiometry Sn 1−x O 2 V x (x=0.05, 0.075, 0.125) have been synthesized by a co-precipitation method. Their structural, vibrational, and nuclear properties have been characterized by x-ray Diffraction, Transmission Electron Microscopy, Energy Dispersive x-ray Spectroscopy, Raman Spectroscopy, and Mössbauer Spectroscopy (with 119 Sn probe) at ambient pressure. We also performed high-pressure synchrotron x-ray diffraction experiments. The structural behaviour was studied up to ∼10 GPa under quasi-hydrostatic conditions. It has been found that tin dioxide nanoparticles with V are more compressible than un-doped tin dioxide nanoparticles.