Electronic and Magnetic Properties of ThCo 4 B

ThCo 4 B compound crystallizes in the hexagonal CeCo 4 B type structure. The electronic structure is calculated based on full-potential local--orbital full-relativistic method. The ab initio calculations showed that small magnetic moments (≈ 0.1 µB/atom) are formed on Th and B atoms, antiparallel to the moments on Co atoms equal to 1.55 and 0.43 µ B /atom for Co(2c) and Co(6i), respectively. The densities of states at the Fermi level are equal to 1.3 and 5.4 states/(eV spin f.u.) for spin up and down, respectively. These values are predominated by Co(3d) electrons. Introduction Recently uranium compounds have attracted interest because of many interesting properties such as the Pauli paramagnetism, spin fluctuations, heavy fermions, magnetic ordering, or superconductivity The aim of this paper is to calculate electronic structure of the ThCo 4 B compound based on a spin-polarized ab initio method

Theoretical search for superconductivity in Sc3XB perovskites and weak ferromagnetism in Sc3X (X = Tl, In, Ga, Al)

A possibility for a new family of intermetallic perovskite superconductors Sc3XB, with X = Tl, In, Ga and Al, is presented as a result of KKR electronic structure and pseudopotential phonon calculations. The large values of computed McMillan--Hopfield parameters on scandium suggest appearance of superconductivity in Sc3XB compounds. On the other hand, the possibility of weak itinerant ferromagnetic behavior of Sc3X systems is indicated by the small magnetic moment on Sc atoms in two cases of X =~ l and In. Also the electronic structure and resulting superconducting parameters for more realistic case of boron--deficient systems Sc3XB_x are computed using KKR--CPA method, by replacing boron atom with a vacancy. The comparison of the calculated McMillan--Hopfield parameters of the Sc3XB series with corresponding values in MgCNi3 and YRh3B superconductors is given, finding the favorable trends for superconductivity.Comment: 13 pages, 13 figures. v3 - revise

Electronic properties of CeNiAl4 based on ab initio calculations and XPS measurements

The CeNiAl4 compound crystallizes in an orthorhombic YNiAl4-type structure with a Cmcm space group. The earlier susceptibility data and X-ray photoelectron spectroscopy (XPS) suggested a localized character of the 4f states in CeNiAl4 with a valence state close to a Ce3 ion. In this work we present a combined theoretical and experimental study of the electronic structure for the Kondo dense system CeNiAl4 based on the XPS data and ab initio calculations. Using the band structure calculations the theoretical XPS valence band spectra are evaluated. Below the Fermi energy the total density of states contains mainly 3d states of Ni hybridized with Ce 4f states

The Electronic and Magnetic Properties of YbxGd1-xNi5 Systems

The intermetallic compounds YbxGd1¡xNi5 crystallize in the hexagonal CaCu5-type structure. Based on wide ranging SQUID-type magnetometer, it was shown that the saturation magnetization decreases with growing concentration of ytterbium. The opposite tendency was observed for the Sommerfeld coefficient obtained in the heat capacity measurements. These results are confirmed using ab initio band structure calculations

Competition of ferromagnetism and superconductivity in Sc3InB

We present results of electronic structure calculations for intermetallic perovskite Sc3InB with Full--Potential KKR-LDA method. Sc3InB is very promising candidate for a new superconductor (related to 8K MgCNi3) and can be regarded as a boron-inserted cubic Sc3In, which is a high--pressure allotropic form of the hexagonal weak ferromagnet Sc3In. We predict that cubic Sc3In can be also magnetic, whereas Sc3InB having large DOS in the vicinity of EF exhibits non-magnetic ground state. Estimation of the electron--phonon coupling for Sc3InB gives $\lambda \simeq 1$. Furthermore, the effect of vacancy in Sc3InB{1-x} and antisite disorder in Sc3(In-B) on critical parameters is also discussed in view of KKR--CPA method. All theoretical results support possibility of the superconductivity onset in Sc3InB. Preliminary experimental measurements established the transition temperature close to 4.5 K, with a very abrupt change in susceptibility and a correlated drop of the resistivity when cooling down.Comment: 4 pages, 3 figures. Conference Paper, presented at European Conference Physics of Magnetism'05, 24-27.06.2005, Poznan, POLAND. Reference correcte

Electronic Structure and X-Ray Photoemission Spectra of MPtSn (M = Ti, Zr, Hf)

The electronic structures of the half-Heusler isostructural compounds TiPtSn, ZrPtSn and HfPtSn were calculated and measured applying the X-ray photoemission spectroscopy. The (Ti, Zr, Hf)PtSn compounds have gaps between the occupied valence band and the empty conduction band, calculated as about 0.75, 1.12, and 1.09 eV, respectively. The calculations were done by the full-potential local orbitals method in the framework of the local spin-density approximation and partly also by the full-potential linear mu±n-tin orbitals method by the LmtART code. Experimental X-ray photoemission spectra were measured using photons of en- ergy of 1486.6 eV. The experimental and calculated spectra match quite well except a small shift in the energy scale

Intermediate valence of CeNi2Al3 compound and its evidences: Theoretical and experimental approach

We present measurements of magnetic, transport and electronic properties obtained for polycrystalline CeNi2Al3 intermetallic compound. Magnetic susceptibility χ(T) was investigated in the range from 2 to 700 K, and its behavior is characteristic of a compound with unstable valence, varying between Ce3þ and Ce4þ. In the temperature range down to 2 K there was no trace of magnetic order, no anomalies in the temperature dependence of the specific heat were found. The Sommerfeld coefficient extracted from the linear term of the heat capacity takes a value of γ ¼ 21 mJ/(mol K2). The dependence of S(T) is linear up to about 25 K, which is symptomatic of a thermopower in the Fermi’s liquid regime. The structure of satellites in the Ce(3d) electron spectrum obtained by the X-ray photoelectron spectroscopy (XPS) method indicates that the states of Ce(4f) are of mixed valence character. Analysis of Ce(3d) states based on Gunnarsson-Sch€onhammer theory shows that the energy of hybridization of Ce(4f) states with a conduction band is about 78 meV. For more detailed information about electronic states the fully relativistic band structure was calculated within the density functional theory (DFT) for the first time. Below Fermi’s energy, the density of states is mainly formed by Ni(3d) states hybridized with Ce(4f) ones

Effect of Boron substitution on the superconductivity of non-oxide perovskite MgCNi3

We report synthesis, structural and magnetic (DC and AC) properties of Boron substituted MgCNi3 superconductor. A series of polycrystalline bulk samples Mg1.2C1.6-xBxNi3 (x = 0.0, 0.08 and 0.16) is synthesized through standard solid-state reaction route, which are found to crystallize in cubic perovskite structure with space group Pm3m. Rietveld analysis of observed XRD data show that lattice parameters expand from a = 3.8106 (4) {\AA} for pure, to 3.8164 (2) {\AA} and 3.8173 (5) {\AA} for 5% and 10% Boron substituted samples respectively. DC magnetization exhibited superconducting transition (Tc) at around 7.3 K for pure sample, and the same decreases slightly with Boron substitution. The lower critical field (Hc1) at 2 K is around 150 Oe for pure sample, which increases slightly with Boron substitution. For pure sample the upper critical field (Hc2) being determined from AC susceptibility measurements is 11.6 kOe and 91.70 kOe with 50% and 90% diamagnetism criteria respectively, which decreases to 5.57 kOe and 42.5 kOe respectively for 10% Boron substituted sample. 10% Boron substitution at Carbon site has decreased both the Hc2 and Tc. On the other hand lower critical field (Hc1) at 2 K is slightly increased from around 150 Oe for pure sample, to 200 Oe for 10% Boron substituted sample. Seemingly, the Carbon site Boron substitution induced disorder though has increased slightly the Hc1 but with simultaneous decrease in superconducting transition temperature (Tc) and upper critical field (Hc2). The high relative proportion of Ni in studied MgCNi3 suggests that magnetic interactions are important and non-oxide perovskite structure make it interesting.Comment: 13 Pages Text + Figures: comments/suggestions ([email protected]