共查询到20条相似文献,搜索用时 62 毫秒
1.
Y. Brard C. Michel M. Hervieu N. Nguyen F. Studer A. Maignan B. Raveau F. Boure 《Journal of solid state chemistry》2003,170(2):424-434
The possibility to synthesize layered oxycarbonates, with nominal composition Sr4Fe2−xMnxO6CO3 involving trivalent manganese, with 0≤x≤1.5, is reported for the first time. The structural study of Sr4FeMnO6CO3 using NPD, HREM, Mössbauer and XANES, shows that this phase is closely related to n=3 member of the Ruddlesden–Popper family. It derives from the latter by replacing the middle layer of transition metal octahedra by triangular CO3 groups, with two different “flag” and “coat hanger” configurations. The magnetic order is antiferromagnetic and fundamentally different from the magnetic behavior of Sr4Fe2O6CO3. 相似文献
2.
F. Nakagomi S.W. da Silva V.K. Garg A.C. Oliveira P.C. Morais A. Franco Jr. 《Journal of solid state chemistry》2009,182(9):2423-2429
The influence of the Mg-content on the structural and magnetic properties of cubic MgxFe3−xO4 nanoparticles prepared by combustion reaction was investigated using X-ray diffraction, transmission electron microscopy (TEM), Mössbauer spectroscopy, and Raman spectroscopy. Lattice parameter, nanoparticle size, and cation (Mg2+, Fe3+) distribution were quantified as a function of the Mg-content in the range 0.5≤x≤1.5. We found a mixed-like spinel structure at the smaller x-value end whereas the inverse-like spinel structure dominates samples with larger x-values. Moreover, in the x-value range investigated (0.5≤x≤1.5) we found no change in the quadrupole splitting and isomer shift values, though the hyperfine field decreases as the x-value increases. The splitting of the A1g Raman mode was used to both quantify the Mg2+/Fe3+ contents in the tetrahedral site and obtain the cation distribution in the MgxFe3−xO4 structure. The cation distribution obtained from the Raman data is in very good agreement with the cation distribution obtained from the Mössbauer data. 相似文献
3.
Surendran Vinu Pallian Murikoli Sarun Razia Shabna Upendran Syamaprasad 《Solid State Sciences》2009,11(9):1530-1534
The resistivity of Bi1.6Pb0.5Sr2−xEuxCa1.1Cu2.1O8+δ (0.000 ≤ x ≤ 0.180) superconductor has been measured as a function of temperature and magnetic field. The resistivity shows a glassy behavior even at higher temperatures and magnetic fields for the Eu-doped samples as compared with the Eu free sample. The values of glass-transition temperature [Tg], magnetic field dependent activation energy [U0(B)] and the temperature and magnetic field dependent activation energy [U0(B,T)] are found to be maximum for optimal doping levels (x = 0.135) which shows that the flux lines are effectively pinned in this sample. Also for temperatures below the superconducting transition temperature (TC), a scaling of measured resistivity curves in magnetic field (B = 0.4 and 0.8 T) is obtained and this scaling is quite useful for better understanding of the behavior of the flux vortices in high temperature superconductors. 相似文献
4.
Studies on the magnetic properties of the molecular antiferromagnetic material {N(n-C5H11)4[MnIIFeIII(ox)3]}∞, carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mössbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Néel temperature and short-range correlations persisting high above TN. It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (MnII–ox–FeIIIA–...) and (MnII–ox–FeIIIB–...), where different responses of the FeIIIA and FeIIIB spin sites towards an external magnetic field might be responsible for the observation of the uncompensated magnetization in this compound at T < TN. The present magnetic system is an S = 5/2 2-D Heisenberg antiferromagnet system with the intralayer exchange parameter J/kB = −3.29 K. A very weak interlayer exchange interaction was anticipated from the spin wave modeling of the magnetic heat capacity for T < 0.5TN. The positive sign of the coupling between the layers has been concluded from the Mössbauer spectrum in the applied magnetic field. Frustration in the magnetic interactions gives rise to the uncompensated magnetic moment in this compound at low temperatures. 相似文献
5.
Crystal structure, redox, and magnetic properties for the Pr1−xSrxFeO3−δ solid-solution phase have been studied. Oxidized samples (prepared in air at 900°C) crystallize in the GdFeO3-type structure for 0≤x≤0.80, and probably in the Sr8Fe8O23-type (unpublished) structure for x=0.90. Reduced samples (containing virtually only Fe3+) crystallize as the perovskite aristotype for x=0.50 and 0.67 with randomly distributed vacancies. The Fe4+ content increases linearly in the oxidized samples up to x≈0.70, whereupon it stabilizes at around 55%. Antiferromagnetic ordering of the G type is observed for oxidized samples (0≤x≤0.90) which show decreasing Néel temperature and ordered magnetic moment with increasing x, while the Néel temperature is nearly constant at 700 K for reduced samples. Electronic transitions for iron from an average-valence state via charge-separated to disproportionated states are proposed from anomalies in magnetic susceptibility curves in the temperature ranges 500–600 K and 150–185 K. 相似文献
6.
Ian D. Fawcett Gabriel M. Veith Martha Greenblatt Mark Croft Israel Nowik 《Solid State Sciences》2000,2(8)
The SrMn1−xFexO3−δ (x=1/3, 1/2, 2/3) phases have been prepared and are shown by powder X-ray and neutron (for x=1/2) diffraction to adopt an ideal cubic perovskite structure with a disordered distribution of transition-metal cations over the six-coordinate B-site. Due to synthesis in air, the phases are oxygen deficient and formally contain both Fe3+ and Fe4+. Magnetic susceptibility data show an antiferromagnetic transition at 180 and 140 K for x=1/3 and 1/2, respectively and a spin-glass transition at 5, 25, 45 K for x=1/3, 1/2 and 2/3, respectively. The magnetic properties are explained in terms of super-exchange interactions between Mn4+, Fe(4+δ)+ and Fe(3+)+. The XAS results for the Mn-sites in these compounds indicate small Mn-valence changes, however, the Mn-pre-edge spectra indicate increased localization of the Mn-eg orbitals with Fe substitution. The Mössbauer results show the distinct two-site Fe(3+)+/Fe(4+δ)+ disproportionation in the Mn- substituted materials with strong covalency effects at both sites. This disproportionation is a very concrete reflection of a localization of the Fe-d states due to the Mn-substitution. 相似文献
7.
Mitsuharu Tabuchi Satoshi Tsutsui Christian Masquelier Ryoji Kanno Kazuaki Ado Ichiro Matsubara Saburo Nasu Hiroyuki Kageyama 《Journal of solid state chemistry》1998,140(2):1550
The magnetic properties of several LiFeO2polymorphs (different cation arrangements in a cubic close-packed oxygen structure) have been examined by magnetic susceptibility measurements and Mössbauer spectroscopy. Samples with relatively low ferromagnetic impurity levels have been obtained by hydrothermal reaction of FeCl3·6H2O or FeOOH with LiOH·H2O and subsequent annealing in air.α-NaFeO2with no detectable ferromagnetic impurity has been obtained by hydrothermal reaction ofα-FeOOH and NaOH. Whileα-NaFeO2revealed only one anomaly at 11 K (Néel point) in the magnetic susceptibility–temperature curves, each LiFeO2sample shows two anomalies (40–50 and 90–280 K). Mössbauer data confirm that iron is present in the high-spin 3+ state according to the values of the internal field at 4.2 K and isomer shifts at 300 K. The relationship between the cation arrangements and the Néel temperature is discussed for LiFeO2. 相似文献
8.
With the exception of FeRh2S4, powder samples of all systems studied have been obtained as spinel phase without essential impurities. The lattice constants follow Vegard's law. From the Seebeck coefficients and the Mössbauer spectra the valence distribution Cu1+1−xFe2+2x−1Fe3+1−x[Me3+2]X2−4 is derived for 0.5 x 1, while there is only Fe3+ present for 0 < x 0.5. Samples with the overall composition FeRh2S4 contain mostly Rh2S3 and iron sulfide phases, but less than 20% of a spinel phase. 相似文献
9.
The magnetic and electric transport properties of La1−xBaxCoO3 (0<x≤0.50) have been studied systematically. Two effects of substitution divalent ions on the spin-state transition of Co3+ have been differentiated for the substitution of Ba2+ for La3+ in La1−xBaxCoO3. The first is the transition from low-spin state to high-spin state due to lattice expansion, and the second is the transition from low-spin state to intermediate-spin state caused by the strong hybridization between ligand (oxygen) 2p and Co 3d orbital with introduction of holes in the oxygen 2p orbital. Based on the two different spin-state transition mechanisms and experimental results, a phase separation model has been developed and a very detailed magnetic and electric phase diagram of La1−xBaxCoO3 has been constructed. 相似文献
10.
Kenji Ishikawa Kenji Metoki Hiroshi Miyamoto 《Journal of solid state chemistry》2009,182(8):2096-2103
Variation of the phases of Nd2NiO4+δ with the excess oxygen concentration δ has been examined at room temperature in the range 0.067≤δ≤0.224 using the X-ray powder diffraction technique. The phases observed at room temperature are orthorhombic-I (0.21<δ≤0.224), orthorhombic-IV (0.175<δ≤0.21), orthorhombic-II (0.15<δ≤0.175), orthorhombic-II+quasi-tetragonal-I (0.10<δ≤0.15), and quasi-tetragonal-I (0.067<δ≤0.10). 相似文献
11.
For La1−xThxNbO4+x/2, three phases with broad homogeneity regions occur, for 0.075 ≤ x ≤ 0.37, 0.41 < x < 0.61, and 0.65 ≤ x ≤ 0.74. All are related to the scheelite structure type, with at least the first exhibiting an incommensurate structural modulation. An analogous structurally modulated phase was found for LaNb1−xWxO4+x/2 for 0.11 ≤ x ≤ 0.22. Additional phases occur at La0.2Th0.8NbO4.4 and LaNb0.4W0.6O4.3. The electrical conductivity and the direction and wavelength of the structural modulation have been characterized for the La1−xThxNbO4+x/2 phase with 0.075 ≤ x ≤ 0.37. 相似文献
12.
Mourad Hidouri Alain Wattiaux Léopold Fournés Jacques Darriet Mongi B. Amara 《Comptes Rendus Chimie》2011,14(10):904-910
Na2Mn2(1 − x)Cd2xFe(PO4)3 (0 ≤ x ≤ 1) phosphates were prepared by solid state reaction and characterized by powder X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy. The X-ray diffraction patterns indicated the formation of a continuous solid solution which crystallizes in the alluaudite structural type characterized by the general formula X(2)X(1)M(1)M(2)2(PO4)3. The cation distribution, deduced from a structure refinement of the x = 0, 0.5 and 1 compositions, is ordered in the X(2) sites and disordered in the remaining X(1), M(1) and M(2) sites. The magnetic susceptibility study revealed an antiferromagnetic behaviour of the studied compounds. The 57Fe Mössbauer spectroscopy confirmed the structural results and proved the exclusive presence of Fe3+ ions. 相似文献
13.
Mössbauer spectra of the Fe1+xV2−xO4 spinel solid solutions are taken to investigate the cation distribution. Room temperature spectra can be interpreted by assuming that the cation distribution is represented approximately as Fe2+[Fe3+xV3+2−x]O4 for 0 x 0.35 and Fe3+[Fe2+Fe3+x−1V3+2−x]O4 for 1 x 2 and the ionic valence arrangement changes from the 2-3-3 type (Fe2+[Fe3+xV3+2−x]O4) to the 3-2-3 one (Fe3+[Fe2+V3+]O4) in the range 0.35 x 1. Fe2VO4 is found to be 3-2-3 spinel, Fe3+[Fe2+V3+]O4. Its paramagnetic spectrum at 473°K is, however, composed of a broad single line with isomer shift value of 0.61 mm/sec relative to stainless steel, in which the line splitting due to the ferric and ferrous ions is rendered indistinguishable. 相似文献
14.
V. A. Morozov B. I. Lazoryak A. P. Malakho K. V. Pokholok S. N. Polyakov T. P. Terekhina 《Journal of solid state chemistry》2001,160(2):377
The double sodium and iron phosphate Na3Fe(PO4)2 was synthesized and studied by the XRD method, the second harmonic generation technique, and Mössbauer and IR spectroscopy. The compound crystallizes into a monoclinic system (space group C2/c) with unit cell parameters a=9.0736(2) Å, b=5.0344(1) Å, c=13.8732(3) Å, β=91.435(2)° and is found to be related to the K3Na(SO4)2 structure type. The crystal structure was determined by Rietveld analysis (Rwp=5.86, RI=2.03). Iron cations occupy the M (Na) position while sodium cations occupy the X (K) and Y (K) positions of the glaserite-like structure. Mössbauer spectroscopy shows the presence of high-spin Fe3+ in octahedral coordination. 相似文献
15.
C. Ma J.-Q. Yan K.W. Dennis R.W. McCallum X. Tan 《Journal of solid state chemistry》2009,182(11):3013-3020
Polycrystalline samples of the Lu1−xLaxMn2O5 solid solution system were synthesized under moderate conditions for compositions with x up to 0.815. Due to the large difference in ionic size between Lu3+ and La3+, significant changes in lattice parameters and severe lattice strains are present in the solid solution. This in turn leads to the composition dependent thermal stability and magnetic properties. It is found that the solid solution samples with x≤0.487 decompose at a single well defined temperature, while those with x≥0.634 decompose over a temperature range with the formation of intermediate phases. For the samples with x≤0.487, the primary magnetic transition occurs below 40 K, similar to LuMn2O5 and other individual RMn2O5 (R=Bi, Y, and rare earth) compounds. In contrast, a magnetic phase with a 200 K onset transition temperature is dominant in the samples with x≥0.634. 相似文献
16.
Fernanda M. Da Costa Robert Greatrex Norman N. Greenwood 《Journal of solid state chemistry》1977,20(4):381-389
The magnetic, electronic, and structural properties of the solid solutions LaxSr1−xRuO3 and LaxCa1−xRuO3 have been studied by 99Ru Mössbauer spectroscopy and other techniques. The LaxCa1−xRuO3 phases are reported for the first time and have been shown by powder X-ray diffraction measurements to be orthorhombically distorted perovskites. Electrical resistivity measurements on compacted powders show that all the phases are metallic with p 10−3, ohm-cm. Progressive substitution of Sr2+ by La3+ in ferromagnetic SrRuO3 leads to a rapid collapse of the magnetic hyper-fine splitting at 4.2°K. For x = 0.25 some ruthenium ions still experience a magnetic field but for 0.4 x 0.75 only single, narrow resonance lines are observed, consistent both with the complete removal of the ferromagnetism and with the presence of an averaged ruthenium oxidation state in each phase, i.e., Lax3+Sr1−x2+Ru(4−x)+O3 rather than Lax3+Sr1−x2+Rux3+Ru1−x4+O3. LaRuO3 and CaRuO3 both give essentially single-line spectra at 4.2°K, indicating that the ruthenium ions in these oxides are not involved in long-range antiferromagnetic order but are paramagnetic. The solid solutions LaxCa1−xRuO3 (0 < x 0.6) give sharp symmetrical singlets with chemical isomer shifts (relative to the Ru metal) which move progressively from the value characteristic of Ru4+ (−0.303 mm sec−1) toward the value for Ru3+ (−0.557 mm sec−1), consistent with the presence of intermediate ruthenium oxidation states in these phases also. 相似文献
17.
Anis Saad A.K. Fedotov I.A. Svito A.V. Mazanik B.V. Andrievsky A.A. Patryn Yu.E. Kalinin A.V. Sitnikov 《Progress in Solid State Chemistry》2006,34(2-4):139
The influence of the composition on the AC carrier transport of the composite films containing ferromagnetic CoFeZr nanoparticles in amorphous aluminium oxide matrix has been investigated. The films 3–5 μm in thicknesses and with variable composition 30 at.% < X < 60 at.% were sputtered on a single substrate from the compound target in the chamber with argon–oxygen gas mixture. TEM and SEM measurements and Mössbauer spectroscopy data have shown that all the studied films of (Co0.45Fe0.45Zr0.10)X(Al2O3)1 − X with 30 at.% < X < 65 at.% have revealed the structure with crystalline granular metallic alloy (with particles of a few nanometers in size) and amorphous alumina. AC conductance measurements were performed over the frequency range 102–106 Hz at temperatures from 80 to 330 K. DC conductance measurements have been carried out for this temperature region also. The presence of two critical regions for the metallic fraction (X1 = 33–40% and X2 = 50–55%), where diagram “electric property–composition” exhibited pronounced peculiarities, has been confirmed. A qualitative structural model of nanocomposite was offered to explain this behavior. In accordance with the model, the first critical region at X1 is associated with a shift of percolation threshold due to the formation of oxide layer on metallic nanoparticles, owing to the presence of oxygen in gas ambient during the sputtering process. The second critical region of the composition at X2 is ascribed to the formation of percolation net of magnetic metallic nanoparticles in the dielectric amorphous alumina matrix. 相似文献
18.
E. Pollert J. Hejtmnek K. Kní
ek M. Mary
ko J. P. Doumerc J. C. Grenier J. Etourneau 《Journal of solid state chemistry》2003,170(2):368-373
The electric and magnetic properties of the perovskites Nd0.8Na0.2Mn(1−x)CoxO3 (0x0.2) prepared by the usual ceramic procedure were investigated. The insulator-to-metal-like (IM) transition, closely related to a ferromagnetic arrangement, was revealed for the composition of x=0.04 and a similar tendency was detected for x=0. The insulating behavior persists down to low temperatures for higher contents of cobalt ions in spite of the transition to the bulk ferromagnetism. The properties are interpreted in terms of the steric distortion, tilting of the Mn(Co)O6 octahedra and the double-exchange interactions of the type Mn3+–O2−–Mn4+and Mn3.5+δ–O2−–Co2+, respectively. Presence of antiferromagnetic domains in the ferromagnetic matrix for the most of cobalt-substituted samples is supposed. 相似文献
19.
Oxypnictides of the type PrOFe1−xCoxAs (x≤0.3) were synthesized for the first time by the sealed tube method. All the compounds were found to be monophasic and crystallize in the tetragonal ZrCuSiAs type structure (space group=P4/nmm) and the lattice parameters (a and c) decrease with increase in cobalt content. Mössbauer measurements of the compounds indicate low spin Fe2+ in tetrahedral coordination. Resistivity and magnetization studies reveal superconducting transitions in compounds with ‘x’=0.05, 0.10 and 0.15, with maximum transition temperature (Tc) at ∼14 K in the compound with ‘x’=0.1. The variation of resistivity with temperature under different magnetic field has been studied to estimate the upper critical field (Hc2) (∼50.2 T for the ‘x’=0.1 composition). The Seebeck and Hall coefficient (RH) suggests electron type charge carriers in these compound and the charge carrier density increases with increase in Co-doping. 相似文献
20.
V. A. Morozov K. V. Pokholok B. I. Lazoryak A. P. Malakho A. Lachgar O. I. Lebedev G. Van Tendeloo 《Journal of solid state chemistry》2003,170(2):411-417
A new strontium iron oxophosphate SrFe3(PO4)3O was synthesized by the solid state method and its structure was studied by single-crystal X-ray and electron diffraction, high-resolution electron microscopy, Mössbauer and IR spectroscopy. The compound crystallizes in a monoclinic system (space group P21/m) with unit-cell parameters: a = 7.5395(7), b = 6.3476(7) c = 10.3161(13) Å, β = 99.740(9)°. The structure of SrFe3(PO4)3O represents a new structural type and is made up of isolated PO4 tetrahedra and FeOn polyhedra connected via common vertices and edges to form a 3D framework. Iron cations occupy three crystallographically independent sites with different oxygen environment: Fe1 and Fe2 occupy two octahedral sites, and Fe3 is five-coordinated. Two particularities of this structure are remarkably mentioned: the isolated {FeO6}n octahedral chains along the b direction and the five coordinated environment for the Fe3 position. Mössbauer spectroscopy confirmed the presence of only high-spin Fe3+ cations in two types of coordination environment. The IR-data show the presence of only PO43− groups. 相似文献