Re-entrant spin glass transition in LiCr0.175mn1.825O4 spinel

Magnetic properties of Cr3+ substituted LiMn2O4 spinel have been investigated by measuring both temperature and field dependence of DC magnetization, as well as temperature dependence of AC susceptibility. Obtained results point to the reentrant spin glass behavior in the low temperature region where system undergoes long range antiferromagnetic transition at TN=42 K followed by the spin glass transition at Tf=22 K. High temperature behavior is of the Curie-Weiss type with effective magnetic moment corresponding to the sample's chemical composition.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Structural and magnetic properties of mechanochemically synthesized LaFe1-xCrxO3 (x = 0.5 and 0.75)

Perovskite oxides with the composition LaFe1-xCrxO3 (x = 0.5 and 0.75) have been studied. The samples have been prepared using the mechanochemical treatment. A mixture of crystalline La(OH)3, Fe2O3 and Cr2O3 powders in stoichiometric ratio was mechanochemically treated in a planetary ball mill up to 40 h of milling. The mechanochemical formation of the LaFe1-xCrxO3 perovskite phase was followed by X-ray diffraction and magnetization measurements. The Rietveld refinement of the XRD data shows that the compounds crystallize in an orthorhombic perovskite structure with a random distribution of the Fe and Cr cations at the B sublattice. All structural and microstructural parameters were analyzed. In addition, magnetic measurements for LaFe0.5Cr0.5O3 show clear antiferromagnetic ordering bellow 250 K, which supports above conclusion of random distribution of Fe and Cr cations

Influence of Ni2+/Co2+ ratio in electrolyte on morphology, structure and magnetic properties of electrolytically produced Ni−Co alloy powders

Nickel−cobalt (Ni−Co) alloy powders were produced galvanostatically by using sulphate electrolytes with various ratios of Ni2+/Co2+ (mole ratios). The morphology, phase structure, chemical composition and magnetic properties were examined by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic emission spectrometer (AES), and SQUID-based magnetometer, respectively. Morphology of the particles changed from cauliflower-like and dendritic to coral-like and spongy-like ones with increasing Ni2+/Co2+ ratio from 0.25 to 4.0. XRD analysis of the Ni−Co powders revealed that the decrease of Ni2+/Co2+ ratios (the increase of Co content) caused a change of structure from face centered cubic (FCC) obtained for the ratios of 4.0, 1.5 and 0.67 to a mixture of FCC and hexagonal closed-packed (HCP) phases for the ratio of 0.25. The increasing content of nickel led to change of mechanism of electrolysis from irregular (up to ~40 wt.% Ni in the electrolytes) to close to equilibrium (between ~40 and 60 wt.% Ni in the electrolytes) and anomalous co-deposition (over 60 wt.% Ni in the electrolytes) type. All of the obtained Ni−Co alloy samples behaved as soft magnetic materials while their magnetic parameters showed immediate composition dependence since both coercivity and saturation magnetization almost linearly increased with increase of the Co content

Magnetic Properties of Cr(III) and Fe(III) Ions in Hexaaqua-Nitrate-Trihydrates

The manuscript contains new measurements and calculations of magnetic susceptibility of Cr(III) and Fe(III) ions in hexaaqua-nitrate-trihydrate. The magnetic properties of the ion M=Cr(III), Fe(III) in hexaaqua-nitrate-trihydrate M(H2O)6(NO3)3·3H2O were studied from the temperature dependence of magnetic susceptibility determined using the SQUID susceptometer, within the temperature range 4 K ≤ T ≤ 290 K. The detected deviation from the CurieWeiss law is explained by the splitting of the ground state energies of the magnetic ions under the influence of the crystalline field (splitting in the zero field) and the contribution of the temperature independent Van-Vleck paramagnetism

Effects of fluorination on the structure, magnetic and electrochemical properties of the P2-type NaxCoO2 powder

The main goal of this research has been to investigate for the first time the effects of fluorination on the crystal structure, magnetic, and electrochemical properties of the P2-type NaxCoO2 powder. Sodium cobalt oxide with a P2-type structure is synthesized by a modified solid-state reaction consisting of alternating processes of rapid heating up to 750 °C and rapid cooling to the room temperature. The obtained powder is fluorinated using a gas-solid reaction with NH4HF2 as fluorinating agent. Fluorination causes a decrease of sodium content in the parent phase with the concurrent formation of the minor phases of Na2CO3 and NaF. The structure of NaxCoO2 in both powders is refined in P63/mmc space group. The results of the Rietveld refinement combined with the findings from the XPS measurements confirm the Na0.76CoO2 and Na0.44CoO1.96F0.04 stoichiometries for the pristine and fluorinated powders, respectively, which indicates that 4 at.% of fluorine ions per formula unit are incorporated in the structure. Preliminary electrochemical investigations have revealed an improved charge/discharge performance. The influence of fluorination on morphology and magnetic properties has also been examined.Supporting information: [https://hdl.handle.net/21.15107/rcub_dais_5970]Published version: [https://hdl.handle.net/21.15107/rcub_dais_3980

A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions

In order to study the effect of Fe cation substitution on the local structure, defect formation, and hyperfine interactions in ZnO, Mössbauer spectroscopy measurements of the microwave processed Zn1−xFexO (x=0.05, 0.10, 0.15, and 0.20) nanoparticles, together with ab initio calculations, were performed. Complementary information on the distribution of particle size and morphology, as well as magnetic properties, were obtained by X-ray diffraction, transmission electron microscopy, and squid-magnetometry. The selected model for analyzing the Mössbauer spectra of our samples is a distribution of quadrupole splittings. The fitting model with two Lorentz doublets was rejected due to its failure to include larger doublets. The Fe3+ ions do not yield magnetic ordering in the samples at room temperature. The results from first-principles calculations confirm that the major component of the Mössbauer spectra corresponds to the Fe-alloyed ZnO with Zn vacancy in the next nearest neighbor environment. The magnetic measurements are consistent with the description of the distribution of iron ions over the randomly formed clusters in the ZnO host lattice. While at room temperature all the samples are paramagnetic, magnetic interactions cause a transition into a cluster spin-glass state at low temperatures

Spin Glass Dynamics of Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 Obtained by a Mechanochemical Milling

Spin dynamics of nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 system was studied through the set of diverse magnetic measurements Analysis of the data obtained from magnetic relaxation measurements, memory effect and AC susceptibility experiments pointed to a spin glass like behavior of interacting nanoparticle system14th Czech and Slovak Conference on Magnetism, Jun 06-09, 2010, Kosice, Slovaki

Structural and magnetic properties of mechanochemically synthesized LaFe1-xCrxO3 (x = 0.5 and 0.75)

Perovskite oxides with the composition LaFe1-xCrxO3 (x = 0.5 and 0.75) have been studied. The samples have been prepared using the mechanochemical treatment. A mixture of crystalline La(OH)3, Fe2O3 and Cr2O3 powders in stoichiometric ratio was mechanochemically treated in a planetary ball mill up to 40 h of milling. The mechanochemical formation of the LaFe1-xCrxO3 perovskite phase was followed by X-ray diffraction and magnetization measurements. The Rietveld refinement of the XRD data shows that the compounds crystallize in an orthorhombic perovskite structure with a random distribution of the Fe and Cr cations at the B sublattice. All structural and microstructural parameters were analyzed. In addition, magnetic measurements for LaFe0.5Cr0.5O3 show clear antiferromagnetic ordering bellow 250 K, which supports above conclusion of random distribution of Fe and Cr cations

Spin glass like behaviour of magnetite nanoparticle system obtained by thermal decomposition of acetylacetonate precursor

The research aim was to investigate the magnetic properties of strongly interacting Fe3O4 nanoparticles. Monodisperse nanoparticles were prepared by thermal decomposition of iron (III) acetylacetonate. Transmission electron microscopy pointed to the narrow particle size distribution with the mean particle size of (4.87±1.10) nm. The magnetic properties were studied by means of SQUID magnetometer, with AC and DC measurements carried in the wide range of applied magnetic field, temperature and frequencies. Magnetic characterization proved superparamagnetic behaviour at high, as well as spin glass like (SGL) properties at low temperatures. The experimental fingerprints for SGL behaviour were found in the observed memory effects.Program and the book of abstracts available at: [https://dais.sanu.ac.rs/handle/123456789/175]Twelfth Young Researchers' Conference Materials Sciences and Engineering December 11-13, 2013, Belgrade, Serbi

Magnetic properties of nanostructured SiOo2:Eu3+ powders

Eu-doped silica nanoparticles with different concentrations of europium (3% 6%and 15at.%) were prepared by a hydrothermal procedure. Light scattering measurements of the silica colloids as well as TEM microscopy, revealed a narrow size distribution of the particles, ranging from 5 to 10 nm. X-Ray diffraction showed that all the powders were amorphous. Magnetic susceptibility vs. temperature measurements showed a behavior typical for Eu3+ ions, with a plateau below 60K, and an increase of the mass susceptibility with Eu concentration. The splitting of zero-field cooled (ZFC) and field-coled (FC) susceptibility branches increased with the europium concentration, indicating the presence of interparticle interactions. At temperatures below 40K, a contribution of paramagnetic impurities obeying the Curie law was observed. Heat treatment of the powders at 823K and 1073K increased the magnetic susceptibility. The appearance of a small peak at 70K indicated the presence of small quantities of ferromagnetic EuO in the powders after heating