Crystal and magnetic structure and cation distribution of Mn 2− x V 1+ x O 4 spinels ( x = 0, 1/3 and 1 (original) (raw)
Related papers
Magnetic characterization of spinel
Journal of Physics and Chemistry of Solids, 2008
Li 1+x Mn 2−x O 4 spinels have been prepared by wet route technique in the whole concentration range 0 ≤ x ≤ 1/3. Structural analysis has been performed by X-ray diffraction and scanning electron microscopy and Raman spectroscopy. The investigation of impurity phases by magnetic experiments complete the sample characterization, allowing for a comparison with samples obtained by other chemical routes. The analysis of the intrinsic magnetic properties show that the magnetic interactions are Mn 3+ -O-Mn 3+ interactions in a geometrically frustrated lattice, while the Mn 4+ -Mn 4+ interactions are negligible, with the consequence that the paramagnetic Curie temperature vanishes in the limit x ≃ 1/3 where only Mn 4+ ions remain. A consistent description of both the extrinsic and the intrinsic properties including former investigations of electron paramagnetic resonance has been achieved in relation to the electrochemical properties.
Magnetic properties of the spinel system MgxMn3-xO4 (0 x 2)
HAL (Le Centre pour la Communication Scientifique Directe), 2008
Temperature-dependent studies of the low-field magnetization of the polycrystalline spinel oxide Mg x Mn 3-x O 4 (0 ≤ x ≤ 2) are reported. With the use of Lotgering's model, which is equivalent to the Néel's two-sublattice model, a set of molecular field constants λ AB , λ BB and λ AA , has been obtained for 0 ≤ x ≤ 0.4 from the fit of χ between T C and room temperature. Moreover, this model fits consistently the low-temperature canted-spin angles ψ of the B-sublattice. The Curie temperatures T C , as well as the exchange parameters J AB , J BB and J AA , show that the BB interactions are much greater than AA and AB, which are of the same order, in contrast to the situation usually found in magnetic spinels. As the concentration of the non-magnetic ion Mg 2+ increases at the tetrahedral site (A), T C decreases from 42K (for x = 0) while the ferromagnetic behaviour diminishes at the expense of a magnetic frustration, thus highlighting the great influence of the non-magnetic ions located at the A and B-sites on the magnetic order.
Magnetic properties of the spinel system MgxMn3-xO4 (0 ≤ x ≤ 2)
Boletín de la Sociedad Española de Cerámica y Vidrio, 2008
Temperature-dependent studies of the low-field magnetization of the polycrystalline spinel oxide Mg x Mn 3-x O 4 (0 ≤ x ≤ 2) are reported. With the use of Lotgering's model, which is equivalent to the Néel's two-sublattice model, a set of molecular field constants λ AB , λ BB and λ AA , has been obtained for 0 ≤ x ≤ 0.4 from the fit of χ between T C and room temperature. Moreover, this model fits consistently the low-temperature canted-spin angles ψ of the B-sublattice. The Curie temperatures T C , as well as the exchange parameters J AB , J BB and J AA , show that the BB interactions are much greater than AA and AB, which are of the same order, in contrast to the situation usually found in magnetic spinels. As the concentration of the non-magnetic ion Mg 2+ increases at the tetrahedral site (A), T C decreases from 42K (for x = 0) while the ferromagnetic behaviour diminishes at the expense of a magnetic frustration, thus highlighting the great influence of the non-magnetic ions located at the A and B-sites on the magnetic order.
Mg0.50Cu0.5-xNixFe2O4 Spinel Nanoferrites: Structural, Electrical, Magnetic and Y-K Angle Studies
Journal of Nano Research, 2012
Spinel Nanoferrites of composition Mg 0.50 Cu 0.5-x Ni x Fe 2 O 4 (0.00≤x≤0.50) were synthesized by chemical co-precipitation method. The structural, morphological and magnetically changes due to varying concentrations of metal ions of Cu and Ni in the prepared nanoferrites were studied. XRD confirmed the formation of single phase spinel ferrite with crystalline sizes in between 16-29 nm, and the lattice parameter (a) found to decreases with increase of Ni concentration. Electrical resistivity of the prepared nanoferrites with varying nickel and copper concentrations x observed to follow Arrhenius relation and also exhibited the semiconductor behavior. The magnetic hysteresis curves clearly indicate the soft nature of the prepared samples. Saturation magnetization (M s ) increases with Ni content. This effect is related to the magnetic moments of Ni +2 ions. The Y-K angles increase with increasing Ni content, and suggest a non-collinearity Néel type of ordering of the Y-K type. The increase in the Y-K angles also suggests the increase in triangular spin arrangements on B sites, which subsequently lead to increment in A-B interactions.
Magnetic properties of (Co, Ni, Mn)(3) O-4 spinels
Bol. Soc. Esp. Ceram
Magnetic properties of new materials, based on the general formula Co x Ni y Mn z O 4 (x+y+z= 3), have been investigated as a function of magnetic field and temperature. The behavior observed in the paramagnetic regime (220 K ≤ T ≤ 400 K) shows a direct correlation with the nominal cation concentration. The paramagnetic-ferrimagnetic transition which takes place at T = T c depends on the overall composition, going from T c = 120 K (for Co 0.2 NiMn 1.8 O 4) up to T c = 210 K (for Co 1.2 Ni 0.3 Mn 1.5 O 4). A second transition is observed at lower temperatures, corresponding to a second ordered magnetic sublattice. This second transition takes place at about 60 K (for Co 0.6 NiMn 1.4 O 4), increasing with the cobalt content up to about 160 K. Under an external magnetic field, both transitions merge into a single one, with a characteristic temperature T max , which rapidly decreases with increasing field. Magnetization loops M(H) obtained at 5 K show a typical behavior of soft magnetic materials, with low coercive fields. Low conductivity values were observed at room-temperature, increasing by a factor of 200-1000 at high temperatures (400 C), which make these compounds to be very interesting materials for potential applications as NTCR thermistors.
Physica B-condensed Matter, 2006
The spinel system MnGaxFe1-xCrO4 (x=0.0, 0.25, 0.50, 0.75 and 1.0) was prepared by the solid state sintering method in air at 1523 K. X-ray and neutron powder diffraction measurements were performed on the samples at 295 K for structural characterization. Rietveld refinement of the neutron diffraction data revealed that all the samples of the series possessed cubic symmetry corresponding to the space group Fd3m. The distributions of the four cations Mn, Ga, Fe and Cr over the two sublattices and other crystallographic parameters were found. The lattice constant showed a decrease with increasing Ga content in the system. The magnetic structure at room temperature was found to be ferrimagnetic in the composition range x⩽0.50.
Mg0.50Cu0.5-xNixFe2O4 Spinel Nanoferrites: Structural, Electrical, Magnetic and Y-K Angle Studies
Spinel Nanoferrites of composition Mg 0.50 Cu 0.5-x Ni x Fe 2 O 4 (0.00≤x≤0.50) were synthesized by chemical co-precipitation method. The structural, morphological and magnetically changes due to varying concentrations of metal ions of Cu and Ni in the prepared nanoferrites were studied. XRD confirmed the formation of single phase spinel ferrite with crystalline sizes in between 16-29 nm, and the lattice parameter (a) found to decreases with increase of Ni concentration. Electrical resistivity of the prepared nanoferrites with varying nickel and copper concentrations x observed to follow Arrhenius relation and also exhibited the semiconductor behavior. The magnetic hysteresis curves clearly indicate the soft nature of the prepared samples. Saturation magnetization (M s ) increases with Ni content. This effect is related to the magnetic moments of Ni +2 ions. The Y-K angles increase with increasing Ni content, and suggest a non-collinearity Néel type of ordering of the Y-K type. The increase in the Y-K angles also suggests the increase in triangular spin arrangements on B sites, which subsequently lead to increment in A-B interactions.
Journal of Applied Physics, 2009
We present experimental results of electrical resistivity ͑͒, magnetoresistance ͑MR͒, Seebeck coefficient ͑S͒, and magnetic susceptibility ͑͒ experiments at high temperature on the spinel Mn 2−x V 1+x O 4 series with x =0, 1 3 , and 1, prepared by solid state reaction. The Rietveld analysis of neutron powder diffraction ͑NPD͒ patterns confirm the expected cubic symmetry ͑SG: Fd-3m͒ with cell parameters around 8.5 Å. We also precisely calculate the distribution of Mn/V cations, in the tetrahedral and octahedral sites, for the whole series showing an important degree of inversion. The magnetic susceptibility and electrical transport properties show ferrimagnetic and semiconductor behaviors, respectively. A large difference detected between the activation energies for S and indicates the presence of small polarons and the temperature dependence of is well fitted with the nonadiabatic polarons model. All the samples present positive MR at room temperature, in particular, the highest value ͑around 1%͒ was observed in the MnV 2 O 4 sample.
Magnetic properties of (Co, Ni, Mn)3O4 spinels
Boletín de la Sociedad Española de Cerámica y Vidrio, 2004
Magnetic properties of new materials, based on the general formula Co x Ni y Mn z O 4 (x+y+z= 3), have been investigated as a function of magnetic field and temperature. The behavior observed in the paramagnetic regime (220 K ≤ T ≤ 400 K) shows a direct correlation with the nominal cation concentration. The paramagnetic-ferrimagnetic transition which takes place at T = T c depends on the overall composition, going from T c = 120 K (for Co 0.2 NiMn 1.8 O 4) up to T c = 210 K (for Co 1.2 Ni 0.3 Mn 1.5 O 4). A second transition is observed at lower temperatures, corresponding to a second ordered magnetic sublattice. This second transition takes place at about 60 K (for Co 0.6 NiMn 1.4 O 4), increasing with the cobalt content up to about 160 K. Under an external magnetic field, both transitions merge into a single one, with a characteristic temperature T max , which rapidly decreases with increasing field. Magnetization loops M(H) obtained at 5 K show a typical behavior of soft magnetic materials, with low coercive fields. Low conductivity values were observed at room-temperature, increasing by a factor of 200-1000 at high temperatures (400 C), which make these compounds to be very interesting materials for potential applications as NTCR thermistors.
Journal of physics. Condensed matter : an Institute of Physics journal, 2017
Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic [Formula: see text] indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in [Formula: see text] system and its consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment...