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1.
The first principles within the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) approach were applied to study the new mixed valence compound Ba2F2Fe1.5S3. The density of states, the electronic band structure and the spin magnetic moment are calculated. The calculations reveal that the compound has an antiferromagnetic interaction between the FeIII and FeII ions arising from the bridging S atoms, which validate the experimental assumptions that there is a low-dimensional antiferromagnetic interaction in Ba2F2Fe1.5S3. The spin magnetic moment mainly comes from the FeIII and FeII ions with smaller contribution from S anion. By analysis of the band structure, we find that the compound has half-metallic property.  相似文献   

2.
First-principles full potential linearized augmented plane wave (FPLAPW) calculations have been performed to study the electronic structure and the magnetic properties of 3-Cyanobenzo-1,3,2-dithiazolyl,C7H3S2N2. The density of states (DOS), the total energy of the cell, and the spontaneous magnetic moment of C7H3S2N2 were all calculated. The calculations reveal that the low-temperature phase of the compound C7H3S2N2 has a stable metal-antiferromagnetic ground state, and there exists an antiferromagnetically coupled interactions between the dithiazolyl radical(1), which is in good agreement with experiment.  相似文献   

3.
The electronic structure, the metallic and magnetic properties of metal phosphonate Co[(CH3PO3)(H2O)] have been studied by first-principles calculations, which were based on the density-functional theory (DFT) and the full potential linearized augmented plane wave (FPLAPW) method. The total energy, the spin magnetic moments and the density of the states (DOS) were all calculated. The calculations reveal that the compound Co[(CH3PO3)(H2O)] has a stable metallic antiferromagnetic (AFM) ground state and a half-metallic ferromagnetic (FM) metastable state. Based on the spin distribution obtained from calculations, it is found that the spin magnetic moment of the compound is mainly from the Co2+, with some small contributions from the oxygen, carbon and phosphorus atoms, and the spin magnetic moment per molecule is 5.000μB, which is in good agreement with the experimental results.  相似文献   

4.
A small amount of Sc substitution for Y in the antiferromagnetic metal YMn2 results in a paramagnetic metal with a strongly enhanced electronic specific heat. We have studied the electronic structure of YMn2 and Y0.97Sc0.03Mn2 by photoemission spectroscopy. The spectra of YMn2 taken above and below the Néel temperature did not show appreciable difference, and the spectra of YMn2 and Y0.97Sc0.03Mn2 were similar to each other. The photoemission spectra of the antiferromagnetic phase are well explained by band-structure calculation on the antiferromagnetic state while those of the paramagnetic phase are not explained by band-structure calculation on the paramagnetic state. These observations suggest that there are strong antiferromagnetic correlations in the paramagnetic phase. For the paramagnetic phase, agreement between experiment and calculation could be considerably improved by applying a model self-energy correction to the band density of states.  相似文献   

5.
The electronic structure and magnetic properties of new layered oxyselenide compounds La2O3Fe2Se2 and La2O3Co2Se2 are studied by first-principles calculations. Our results indicate that both compounds are Mott-insulators with orbital ordering. The ground states of both compounds are the checkerboard antiferromagnetic states, which are different from the iron pnictide superconductors, although their structures are similar to those of the Fe-As-based superconductors.  相似文献   

6.
The ground states of rare-earth nickelates (RNiO3) are antiferromagnetic insulators except LaNiO3, which is a strongly correlated metal. Rare-earth nickelates (R ≠ La) undergo a sharp transition from a high-temperature paramagnetic metal to a low-temperature antiferromagnetic insulator at finite temperature TMI that increases with the increase in atomic number of the rare-earth ions. The magnetic and resistive transitions are coupled for NdNiO3 and PrNiO3, but independent for the other members of the series. Whether the antiferromagnetic and insulating ground states of nickelates are due to charge ordering, or orbital ordering, it is a matter of current dispute. The present paper intends to explain the difference in the observed ground states of RNiO3 compounds, by calculating their band structure and density of states. The experimentally observed ground states of nickelates have been explained on the basis of mean-field calculation and the correlation effect is incorporated in the dynamical mean-field theory thereof.  相似文献   

7.
The electronic structure and magnetic properties of the Laves phase of LuFe2 with C14, C15, and C36 structures has been investigated using the full-potential linearized augmented plane wave method. In order to study the stability of magnetic phases, nonmagnetic and spin-polarized calculations for ferromagnetic ordering were performed. It is found that the ferromagnetic hexagonal C14 phase is the ground-state structure and the C15 phase is an intermediate state between the C14 and C36 structures. There is an increase in the average magnetic moment on the Fe sites in the order of C15 →C14 →C36 structures, whereas the Lu-moment is not significantly different. We also find that there exist both localized and itinerant d electrons, resulting in antiferromagnetic ordering in the three structures. Their density-of-states, equilibrium volumes, and elastic properties are discussed, which is important for the understanding of the physical properties of LuFe2 and may inspire future experimental research.  相似文献   

8.
L3 X-ray absorption spectroscopic study of Eu firmly establishes that the compound, EuPd2Si2, is a mixed valence system. It is found that the relative intensities of the absorption peaks corresponding to divalent and trivalent europium ions in EuPd2Si2 are a strong function of temperature.  相似文献   

9.
Electronic structure and magnetic properties of perovskite EuZrO3 have been investigated using the ab initio density-functional calculations with local spin density approximation (LSDA) and LSDA+U methods. The results that are obtained reveal that the antiferromagnetic G-type arrangement is more stable than other possible configurations. The ground G-AFM state shows the insulator property with an energy gap of about 0.27 eV at U=0 eV. It is found that the energy gap strongly depends on the correction potential parameter of U due to the strong interaction of the f electrons of Eu in EuZrO3. The spin magnetic moment of Eu ions is predited to be 6.82μB, which is in well agreement with the experimental result of 6.87μB.  相似文献   

10.
蒋青  吴华 《中国物理》2002,11(12):1303-1306
The dielectric constant of an incipient ferroelectric EuTiO3 exhibits a sharp decrease at about 5.5K, at which the antiferromagnetic ordering of the Eu spins simultaneously appears. This fact indicates the existence of a coupling between the magnetism and dielectric properties of EuTiO3. We propose a possible coupling mechanism between the magnetic and electrical subsystems as -g\dsuml \dsum〈i,j〉q2l\vec Si·\vec Sj. In the framework of soft-mode theory, we have obtained analytically a dielectric constant expression related to the spin correlation of nearest neighbours of Eu ions.  相似文献   

11.
The magnetic properties, electronic structure, and optical properties of the filled skutterudite BaFe4Sb12 are calculated by the first-principles full-potential linearized augmented plane wave (FPLAPW) plus local orbital method. It is found that the local spin density approximation (LSDA) method appears more accurate than the generalized gradient approximation (GGA) method in calculating the electronic structures and optical properties of this compound. Furthermore, our calculated lattice constant and spin magnetic moments with the LSDA method are in overall better agreement with experiment. In contrast with recent experiment, our calculations are in good agreement with experimental reflectivity spectra and optical conductivity spectrum.  相似文献   

12.
First principles calculations based on the density functional theory within the local spin density approximation plus U(LSDA + U) scheme, show rhombohedral Bi2FeTiO6 is a potential multiferroic in which the magnetism and ferroelectricity coexist. A ferromagnetic configuration with magnetic moment of 4μB per formula unit has been reported with respect to the minimum total energy. Spontaneous polarization of 27.3 μC/cm2, caused mainly by the ferroelectric distortions of Ti, was evaluated using the berry phase approach in the modern theory of polarization. The Bi-6s stereochemical activity of long-pair and the ‘d0-ness’ criterion in off-centring of Ti were coexisting in the predicted new system. In view of the oxidation state of Bi3+, Fe2+, Ti4+, and O2− from the orbital-resolved density of states of the Bi-6p, Fe-3d, Ti-3d, and O-2p states, the valence state of Bi2FeTiO6 in the rhombohedral phase was found to be Bi3+2Fe2+Ti4+O6.  相似文献   

13.
The ab initio method of the full potential linearized augmented-plane-wave has been used to study the electronic band structure and the ferromagnetic (FM) properties of the organic radical MOTMP. The total and the partial density of states and the atomic spin magnetic moments are calculated. The calculation revealed that MOTMP has a stable ferromagnetic ground state and the spin magnetic moment is 1.0 μB per molecule, which is in good agreement with the experimental value. It is found that the unpaired electrons in this compound are localized in a molecular orbital constituted primarily of π*(NO) orbital and the main contribution of the spin magnetic moment comes from the NO free radical. It is also found that there exists ferromagnetic intermolecular interaction in the compound.  相似文献   

14.
Magnetic susceptibility, heat capacity and electrical resistivity measurements have been carried out on a new ruthenate, La2RuO5 (monoclinic, space group P21/c) which reveal that this compound is a magnetic semiconductor with a high magnetic ordering temperature of 170 K. The entropy associated with the magnetic transition is 8.3 J/mol K close to that expected for the low spin (S=1) state of Ru4+ ions. The low temperatures specific heat coefficient γ is found to be nearly zero consistent with the semiconducting nature of the compound. The magnetic ordering temperature of La2RuO5 is comparable to the highest known Curie temperature of another ruthenate, namely, metallic SrRuO3, and in both these compounds the nominal charge state of Ru is 4+.  相似文献   

15.
We have calculated the equilibrium volume and the density of states (DOS) of Cr2AlC for antiferromagnetic (AFM), ferromagnetic (FM) and paramagnetic (PM) configurations by ab initio total energy calculations. Based on a comparison of the cohesive energies as well as the DOS for all three magnetic configurations we have identified the FM configuration to be metastable. Furthermore, we report the structural characterization of polycrystalline Cr2AlC thin films grown by magnetron sputtering. Our calculated interplanar distances and equilibrium volume for the PM and AFM configurations are in good agreement with our experiment. The charge density distribution suggests that the chemical bonding between Cr and C in Cr2AlC is very similar to the one in cubic CrC.  相似文献   

16.
We report a detailed theoretical calculation of the electronic band structure of CeO2 in cubic and orthorhombic phases under pressure using a tight-binding linear muffin-tin orbital method (TB-LMTO) within local density approximation (LDA). The compressibility behavior of this compound was discussed in the light of the changes occurring in the electronic structure. Apart from the electronic band structure and structural stability calculations, the density of states (DOS) and Fermi energies (Ef) at various pressures are calculated. The calculated lattice parameter, transition pressure, bulk modulus and the pressure-volume relation are found out to be in good agreement with experimental results.  相似文献   

17.
First-principles density functional theory calculations have been carried out to investigate electronic structures of anatase TiO2 with substitutional dopants of N, Nd, and vacancy, which replace O, Ti, and O, respectively. The calculation on N-doped TiO2 with the local density approximation (LDA) demonstrates that N doping introduces some states located at the valence band maximum and thus makes the original band gap of TiO2 smaller. Examining the effect of the strong correlation of Nd 4f electrons on the electronic structure of Nd-doped TiO2, we have obtained the half-metallic ground state with the LDA and the insulating ground state with the LDA+U (Hubbard coefficient), respectively. In addition, the calculation on vacancy-doped TiO2 with the LDA shows that a vacancy can induce some states in the band-gap region, which act as shallow donors.  相似文献   

18.
The electronic structure and magnetic properties of the (2-amino-5-chloropyridinium)2CuBr4 compound were studied using the full potential augmented plane wave plus local-orbitals method (FP-APW+lo) within density functional theory. The Cu atoms are the magnetic centers, magnetic moments originate mainly from the Cu 3d and Br 4p states, leading to a total magnetic moment of 1.00 μB per molecule. There is an important hybridization between the Cu 3d and Br 4p states, which causes the magnetic interactions between the Cu centers to pass through the Br p-orbitals near the Cu atoms. According to the self-consistent total energies, it was found that in the ground state there exist antiferromagnetic interactions for both intraplanar and interplanar magnetic exchange, but the latter is much weaker than the former.  相似文献   

19.
Mechanisms of anomalous magnetic and transport properties in CeTe2 observed recently on single-crystal samples are studied by comparing with the nonmagnetic reference material LaTe2, as well as other typical low carrier-density systems such as Ce monopnictides, doped Eu chalcogenides and Yb4As3. The present system is unique on the point of low-carrier semimetal due to CDW of near perfect nesting, which is shown to be nearly independent of the spin–orbit splitting. The large residual resistivity indicates the giant molecular scattering due to excitonic states forming the distorted Wigner crystal, similar to Yb4As3. At low temperatures, induced magnetic polarons cause unusual novel transport properties with a sharp peak of resistivity without any anomaly on other physical properties. This is attributed to a sharp glassy transition from an antiferromagnetic short-range ordering to the ferromagnetic ordering of the magnetic polarons within each CeTe double layer sandwiching the mono Te layer. It is shown that, similar to Ce monopnictides, the type strong nonlinear p–f mixing is the origin of the main anomalous magnetic properties. Lattice polarons are essential for the stable excitonic states in LaXc2, as well as in CeTe2 in the ferromagnetic state.  相似文献   

20.
The magnetic field effect of a8S7/2-z6P7/2 lines of 151Eu and 153Eu in magnetic fields up to 66.7 mT has been studied by using laser atomic beam spectroscopy. The Zeeman level structures of the europium a8S7/2 and z6P7/2 states in magnetic fields were discussed. The location and intensity of the measured Zeeman transition lines were found in good agreement with the theoretical results.  相似文献   

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