共查询到20条相似文献,搜索用时 31 毫秒
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C. de la Calle M.J. Martínez-Lope V. Pomjakushin F. Porcher J.A. Alonso 《Solid State Communications》2012,152(2):95-99
The title compounds have been synthesized by a citrate technique. The crystal structure of these materials has been studied at room temperature from high-resolution neutron powder diffraction data. In, Ru, and M=Mn,Fe are distributed at random over the metal sites of a C-M2O3 bixbyite-type structure, space group , with for M=Mn and for M=Fe. It is well known that In2O3 is able to dissolve certain amounts of transition metals but, at ambient pressure, the solubility is rather small, lower than in In2?sMsO3. Here, we describe a substantial incorporation of magnetic transition metals into In2O3 of half of the metal positions (), by simple thermal treatment at temperatures in the 1300–1400 °C range. Although a bond-valence study shows unrealistically low valences for Ru ions, which statistically occupy the metal positions, replacing In, the magnetic properties suggest a valence equilibrium Ru3+/M3+?Ru4+/M2+. In2RuFeO6 shows antiferromagnetic interactions below , with a very weak ferromagnetism effect at low temperatures. 相似文献
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A new experimental method for the determination of the Landau–Lifshitz damping parameter, α, based on measurements of the frequency and field dependence of the complex magnetic susceptibility, χ(ω,H)=χ′(ω,H)-iχ″(ω,H), is proposed. The method centres on evaluating the ratio of fmax/fres, where fres is the resonance frequency and fmax is the maximum absorption frequency at resonance, of the sample susceptibility spectra, measured in strong polarizing fields. We have investigated three magnetic fluid samples, namely sample 1, sample 2 and sample 3. Sample 1 consisted of particles of Mn0.6Fe0.4Fe2O4 dispersed in kerosene, sample 2 consisted of magnetite particles dispersed in Isopar M and sample 3 was composed of particles of Mn0.66Zn0.34Fe2O4 dispersed in Isopar M . The results obtained for the mean damping parameter of particles within the magnetic fluid samples are as follows: 〈α(Mn0.6Fe0.4Fe2O4)〉=0.057 with the corresponding standard deviation SD=0.0104; 〈α(Fe3O4)〉=0.1105 with the corresponding standard deviation, SD=0.034 and 〈α(Mn0.66Zn0.34Fe2O4)〉=0.096 with the corresponding standard deviation, SD=0.037. 相似文献
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In Cr-doped MgAl2O4 most of the Cr3+-ions occupy normal B-sites. In addition to this axial center we report here the presence of an orthorhombic Cr3+-center. The ESR-spectra of this new center can be described by the spin Hamiltonian:, with S=3/2. The principal axes of the center are along [111]=Z, and . The values of the parameters are: gz=1·950±0·005, gx=gy=1·915±0·015, D=+0·903cm?1±0·003 cm?1 and E=+0·084 cm?1±0·005 cm?1. The intensity of the lines is about ten times lower than that of the axial Cr3+-center. 相似文献
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A.V. Bogach G.S. Burkhanov O.D. Chistyakov V.V. Glushkov S.V. Demishev N.A. Samarin Yu.B. Paderno N.Yu. Shitsevalova N.E. Sluchanko 《Journal of magnetism and magnetic materials》2006
A comprehensive and high-precision magnetoresistance (MR) Δρ/ρ(H,T) and magnetization M(H,T) measurements have been carried out for two well known and archetypal magnetic strongly correlated electron systems—CeAl2 and CeB6. It was shown that the main Brillouin-type component of MR in these magnetic heavy fermion compounds can be consistently interpreted in the frameworks of a simple relation between resistivity and magnetization—Δρ/ρ∼M2 obtained by Yosida [Phys. Rev. 107 (1957) 396]. A local magnetic susceptibility χloc(T,H)=(1/H*(d(Δρ/ρ)/dH))1/2 was deduced directly from this part of MR and compared in details with the data of bulk susceptibility χ(T,H) measurements. Two additional contributions to MR have been also deduced for CeAl2 ((i) linear (∼H) and (ii) nanoscale ferromagnetic components) and applied for a characterization of spin polarons in this magnetic material. The dependencies χloc(T,H) and χ(T,H) obtained in this study for CeB6 and CeAl2 allow us to analyze the H–T magnetic phase diagram in these magnetic heavy fermion compounds. 相似文献
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We study the electrical transport properties of a quantum point contact between a lead and a high Tc superconductor. For this, we use the Hamiltonian approach and non-equilibrium Green functions of the system. The electrical current and the shot noise are calculated with this formalism. We consider dx2−y2, dxy, dx2−y2+is and dxy+is symmetries for the pair potential. Also we explore the s+− and s++ symmetries describing the behavior of the ferropnictides superconductors. We found that for dxy symmetry there is not a zero bias conductance peak and for d+is symmetries there is a displacement of the transport properties. From shot noise and current, the Fano factor is calculated and we found that it takes values of effective charge between e and 2e , this is explained by the diffraction of quasiparticles in the contact. For the s+− and s++ symmetries the results show that the electrical current and the shot noise depend on the mixing coefficient, furthermore, the effective electric charge can take values between 0 and 2e, in contrast with the results obtained for s wave superconductors. 相似文献
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《Radiation measurements》2007,42(4-5):644-647
The tetragonal : persistent luminescence materials were prepared by a solid state reaction. The UV excited and persistent luminescence was observed in the green region centred at 535 nm. Both luminescence phenomena are due to the same ion occupying the single site in the host lattice. The codoping usually reduced the persistent luminescence of :, which differs from the : and : materials. Only the ion enhanced slightly the persistent luminescence. With the aid of synchrotron radiation, the band gap energy of : was found to be about 7 eV that is very similar to those of the : materials. Thermoluminescence results suggested that the ions might act as electron traps, but only the TL peaks created by and can be found in the temperature range accessible. Lattice defects (e.g. oxygen vacancies) are also important, since the same main thermoluminescence peak was observed at about with and without codoping. 相似文献
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First principles calculations based on density functional theory have been employed to study the electronic, magnetic and optical properties of Co3O4 in a cubic normal spinel structure. Exchange and correlation effects between electrons were treated by a B3PW91 hybrid functional, which produced better results than others scheme, such as GGA+U or PBE0 hybrid functionals or mBJ semilocal potential. The work focuses on clarifying the nature of the optical absorption bands, which have motivated various theoretical and experimental works in the literature. The calculated optical absorption spectrum was compared with available experimental data. On the basis of this calculated electronic and magnetic structure, the optical absorption peaks (theoretical and experimental) could be satisfactorily explained in terms of d3d charge transfer transitions between both CO2+→CO2+ and CO3+→CO3+ ions. The calculations also predicted that the crystal field splittings at both octahedral and tetrahedral sites in the Co3O4 compound are of the same magnitude. 相似文献
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In this paper we give a complete classification of pseudo-Einstein real hypersurfaces in complex two-plane Grassmannians G2(Cm+2). As an application of this result we prove that there do not exist Einstein Hopf or D⊥-invariant Einstein real hypersurfaces in G2(Cm+2). 相似文献
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In this paper, first we introduce the full expression for the Ricci tensor of a real hypersurface M in complex two-plane Grassmannians G2(Cm+2) from the equation of Gauss. Next we prove that a Hopf hypersurface in complex two-plane Grassmannians G2(Cm+2) with commuting Ricci tensor is locally congruent to a tube of radius r over a totally geodesic G2(Cm+1). Finally it can be verified that there do not exist any Hopf Einstein hypersurfaces in G2(Cm+2). 相似文献
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