Electronic structure and thermodynamic properties of RNi_{5}Sn (R = La, Ce, Pr, Nd) compounds

The electronic structure, pressure and temperature dependence of thermodynamic properties of RNi5Sn (R = La, Ce, Pr, Nd) compounds are calculated by ab initio full potential local orbital minimum-base(ver. 9 and ver. 14) method. These compounds crystallize in the hexagonal crystal structure (space group P6c/mmc, No. 194). The band calculations were performed in the scalar-relativistic mode for the exchange correlation potentials in the form: of the Perdew-Burke-Ernzerhof general gradient approximation. In this work we present the band structures of LaNi5Sn, CeNi5Sn, NdNi5Sn and PrNi5Sn compounds. The thermodynamic properties (bulk modulus, Debye temperature) are calculated in the Debye-Grüneisen model using the equation of states in the form of Birch-Murnaghan, Poirier-Tarantola and Vinet. Our results have shown that values of thermodynamic properties depend on the method of calculations

Electronic structure of CePtIn and LaPtIn compounds

The electronic structure of the ternary RPtIn (R = La, Ce) compounds, which crystallize in the hexagonal ZrNiAl-type structure, was studied by X-ray photoelectron spectroscopy measurements and calculation using the ab initio methods (linear mu n-tin orbital in the atomic sphere approximation, full potential linear mu n-tin orbital, full potential linear orbital). The results showed that the valence band in these compounds is formed by the Pt 5d and In 5s and 5p states. The band calculations with spin orbit coupling have shown that the Ce 4f peaks consist of two peaks above the Fermi level that correspond to the Ce 4f7=2 and 4f5=2 doublet and wide peaks corresponding to the La 4f states. The analysis of Ce 3d spectra on the basis of the Gunnarsson Schönhammer model gives hybridization of 4f orbitals with the conduction electron band equal to 170 meV

Electronic structure and transport properties of CeNi9In2

We investigated CeNi9In2 compound, which has been considered as a mixed valence (MV) system. Electrical resistivity vs. temperature variation was analysed in terms of the model proposed by Freimuth for systems with unstable 4f shell. At low temperature the resistivity dependence is consistent with a Fermi liquid state with a contribution characteristic of electron-phonon interaction. Ultraviolet photoemission spectroscopy (UPS) studies of the valence band did not reveal a Kondo peak down to 14 K. A difference of the spectra obtained with photon energies of low and high photoionization cross sections for Ce 4f electrons indicated that 4f states are located mainly close to the Fermi energy. The peaks related to f_{5/2}^1 and f_{7/2}^1 final states cannot be resolved but form a plateau between -0.3 eV and the Fermi energy. X-ray photoemission spectroscopy (XPS) studies were realized for the cerium 3d level. The analysis of XPS spectra within the Gunnarsson-Sh\"onhammer theory yielded a hybridization parameter of 104 meV and non-integer f level occupation, being close to 3. Calculations of partial densities of states were realized by a full potential local orbital (FPLO) method. They confirm that the valence band is dominated by Ni 3d states and are in general agreement with the experiment except for the behavior of f-electrons.Comment: 10 pages, 5 figure

Electronic structure of CePtIn and LaPtIn compounds

The electronic structure of the ternary RPtIn (R = La, Ce) compounds, which crystallize in the hexagonal ZrNiAl-type structure, was studied by X-ray photoelectron spectroscopy measurements and calculation using the ab initio methods (linear mu n-tin orbital in the atomic sphere approximation, full potential linear mu n-tin orbital, full potential linear orbital). The results showed that the valence band in these compounds is formed by the Pt 5d and In 5s and 5p states. The band calculations with spin orbit coupling have shown that the Ce 4f peaks consist of two peaks above the Fermi level that correspond to the Ce 4f7=2 and 4f5=2 doublet and wide peaks corresponding to the La 4f states. The analysis of Ce 3d spectra on the basis of the Gunnarsson Schönhammer model gives hybridization of 4f orbitals with the conduction electron band equal to 170 meV

Mixed-valence state in Yb2CuGe6

We present here temperature dependent X-ray photoemission measurements on polycrystalline Yb2CuGe6. The analysis of these data shows the change in the effective valence, determined directly from the 4f intensity ratio, as a function of temperature

Size effects in antiferromagnetic NiO nanoparticles

X-ray and neutron diffraction as well as magnetometric methods were used in order to investigate crystal and magnetic structure together with magnetic properties of nickel oxide NiO obtained from thermal decomposition of Ni(OH)$_{2}$. It has been found that crystal unit cell volume and crystal unit cell deformation parameter decrease with increasing decomposition temperature $T_{d}$ while grain size increases. The results of magnetization, magnetic susceptibility and neutron diffraction measurements reveal a formation of antiferromagnetic order with uncompensated magnetic moment below the Néel temperature. Magnetization together with coercive field decreases with increasing $T_{d}$. The neutron diffractogram of sample obtained at 240°C indicates broadening of both the peaks of nuclear and magnetic origin. The magnetic ordering may be described by a propagation vector $k = \left [ \frac{1}{2}, \frac{1}{2}, \frac{1}{2} \right ]$

Electronic structure of TmPdIn

Electronic structure of a ternary TmPdIn compound, which crystallizes in the hexagonal ZrNiAl-type structure, was studied by X-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Density of states in the valence band was calculated by means of the augmented plane wave/local orbital method based on density functional theory. The results showed that the valence band is formed mainly of Tm 4f and Pd 4d states. In the ultraviolet photoemission spectra one can distinguish Pd 4d maximum and Tm 4f multiplet peaks, which are displaced with respect to those of pure Tm

Mechanisms of Electrical Conductivity in Y(1-x)CaxBa2Cu3O6.1 System

Systematic studies of transport properties in deoxygenated Y(1-x)CaxBa2Cu3O6.1 series allowed to propose a diagram of conductivity mechanisms for this system. At intermediate temperature a variable range hopping (VRH) in 2 dimensions prevails. At lower temperature VRH in the presence of a Coulomb gap for smaller x and VRH in 2 dimensions for larger x are found. In a vicinity of superconductivity we observe conductivity proportional to \sqrt{T}. Thermally activated conductivity dominates at higher temperature. This diagram may be universal for the whole family of undoped high Tc related cuprates.Comment: 5 page

Influence of Co doping on crystal and magnetic properties of Gd_{2}Cu_{2}In

Physical properties of $Gd_2Cu_{2 - x}Co_{x}In$ (x = 0.1, 0.2, 0.3) samples are investigated. The paper brings results of X-ray diffraction, magnetometric as well as specific heat studies. It was found that only sample with x = 0.1 exhibits desired crystal structure. Other compositions show existence of impurities due to lack of dissolution Co atoms. For $Gd_2Cu_{1.9}Co_{0.1}In$ sample the Curie temperature of 92.5 K was evidenced. Thus, an enhancement of ferromagnetic correlations with comparison to $Gd_2Cu_2In$ sample was evidenced. It was found that $Gd_2Cu_{1.9}Co_{0.1}In$ sample exhibits magnetocaloric effect within broad temperature range

Neutron scattering study of TbPtIn intermetallic compound

Neutron diffraction techniques have been used to study the magnetic properties of a TbPtIn single-crystal as a function of temperature and magnetic field. In the absence of an externally applied magnetic field, the compound orders, below approximately 47 K, in an antiferromagnetic structure with propagation vector k=(12,0,12); the magnetic moments were found to be parallel to the [12̄0] direction. Measurements at 4.2 K, with a magnetic field applied along the [12̄0] direction, revealed metamagnetic transitions at approximately 20 kG and 40 kG