Search

The LuPd 2 Si 2 compound is a member of a large group of compounds crystallizing in the ThCr 2 Si 2 tetragonal type of structure. The negative thermal expansion of the lattice parameter c was determined by means of an x-ray diffraction experiment performed at different temperatures between 3 K and 300 K. Temperature of transition to a superconducting state was calculated and experimentally confirmed at 0.6 K. Comparison between results of theoretical calculations based on the local spin density approximation (LSDA) and the generalized gradient approximation methods (GGA) is given in the article. [ABSTRACT FROM AUTHOR]

Abstract: We present a study of structural and electronic properties of YPd5Al2. Specific-heat measurements reveal a relatively low Sommerfeld coefficient of the electronic contribution γ=4.1mJmol−1 K−2. No superconductivity is found down to 0.4K. First-principles electronic-structure calculations based on density-functional theory have been performed and have been compared with available experimental structural and electronic data. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density-functional theory were performed for the first time on RTAl (R=Y, Lu, T=Ni, Cu, Pd) compounds. The electronic density of states and equilibrium volume were studied using the relativistic full-potential APW plus local-orbitals calculations and compared with the experimental data available. [Copyright &y& Elsevier]

Abstract: We present the results of XRD, magnetization, resistivity and specific heat measurements of CeIr2Si2 single crystals for both, the low-temperature α-phase and the high-temperature β-phase, respectively. The α-phase adopts the tetragonal ThCr2Si2-type whereas the β-phase forms in the CaBe2Ge2-type structure. Both the phases remain paramagnetic down to low temperatures, nevertheless both, the magnetization and resistivity exhibit pronounced anisotropy in the whole temperature range of measurements (2–300K). Results of fitting the temperature dependence of the susceptibility within the interconfiguration-fluctuation model point to the Ce valence fluctuating between 3+ and 4+. The α-phase behaves as a Fermi-liquid (FL) at low temperatures whereas the β-phase exhibits non-Fermi-liquid (NFL) features. The results are discussed in context of other similar polymorphic compounds. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density-functional theory were performed on UCoGe, a ferromagnetic superconductor reported recently [N.T. Huy, A. Gasparini, D.E. de Nijs, Y. Huang, J.C.P. Klaasse, T. Gortenmulder, A. de Visser, A. Hamann, T. Gőrlach, H.v. Lőhneysen, Phys. Rev. Lett. 99 (2007) 067006]. The electronic density of states and magnetic properties were studied using the relativistic full-potential APW plus local-orbitals method and the full-potential local-orbitals (FPLO) method, respectively. A stable ferromagnetic ground state was found. The uranium total magnetic moment is quite small (about 0.1μ B) as a result of almost complete cancellation between the spin magnetic moment of 1.2μ B and the opposite orbital magnetic moment of 1.1μ B, resulting from strong spin–orbit coupling at the uranium site. A magnetic moment of 0.4 and 0.2μ B was found at the cobalt site using the APW+lo and the FPLO method, respectively. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density-functional theory were performed for the first time on NpTAl (T=Co, Ni, Rh, Ir and Pt) and NpNiGa. The electronic density of states and equilibrium volume were studied using relativistic full-potential APW plus local-orbitals calculations. The magnetocrystalline anisotropy energy was estimated from total-energy calculations and the a-axis was predicted to be the easy axis of magnetization with the exception of T=Rh. Finally, we employed the LSDA+U method to mimic the orbital polarization and to obtain the correct total magnetic moments in experimental equilibrium. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density-functional theory (DFT) were performed on RPt3Si (R=Pr, Nd, Sm) for the first time. The electronic density of states (DOS) and bonding properties were studied using relativistic full-potential APW plus local orbitals calculations. The crystal-field (CF) splitting was derived for NdPt3Si and SmPt3Si by fitting the temperature-dependent magnetic susceptibility. The starting estimate of the CF parameters for fitting procedure was obtained from first-principles calculations based on DFT. [Copyright &y& Elsevier]

Abstract: A series of isostructural La(FeMn)Si pseudoternaries has been synthesized and characterized by X-ray powder diffraction and microprobe analysis. While the Mn-rich compounds behave like the pure LaMnSi with both and systematically shifted to lower temperatures, the Mn-poor compounds show a steep tail on the low-temperature dependence of the specific heat with a maximum slope for =0.025. An influence-of Mn substitution on the ground state of La(FeMn)Si solid solutions will be discussed in comparison with the results of electronic structure calculations. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetic properties of the intermetallic compounds LuFe6Al6 and UFe6Al6 have been calculated using density functional theory. For scalar relativistic calculations, the FPLO code with coherent potential approximation was used. In the case of R=U with strong spin-orbit coupling at the uranium site, the APW+lo (WIEN2k) code and supercell technique was employed. The calculated total magnetic moment of 10.03μB for LuFe6Al6 is in very good agreement with the experimental value of 10.0μB for the saturated moment. In the case of UFe6Al6, a pronounced spin and orbital moment at the U site was found from supercell calculations. The calculated total magnetic moment is in fair agreement with the experimental result of 9.7μB for UFe6Al6 taking into account the limitation of the supercell calculations, including spin–orbit coupling. The theoretical electronic density of states and Sommerfeld coefficients have been obtained and are compared with the experimental results available. The site-resolved magnetic moments of the RFe6Al6 compounds are also provided. [Copyright &y& Elsevier]

Abstract: A new method for calculations of crystal field (CF) interaction in alloys containing rare earths (4f electron CF) has been developed. The method is based on density-functional theory (DFT) and uses the full-potential local-orbitals (FPLO) method combined with the coherent-potential approximation (CPA). The method is successfully applied to calculate the CF interaction in RENi4Al alloys. [Copyright &y& Elsevier]

Abstract: First-principles calculations of electronic structure and magnetic properties based on density-functional theory were performed for MnFeP1− x Si x (0.44⩽x⩽0.60) alloys which are considered as promising magnetocaloric refrigerants. We used the full-potential APW+lo method and treated the random order of P(Si) atoms in the ZrNiAl-type structure in a virtual-crystal approximation. A non-monotonic behavior of the alloy magnetization as a function of x was obtained, in qualitative agreement with experiment, and explained in terms of the spin-polarized densities of states. [Copyright &y& Elsevier]

Abstract: We have studied influence of the Pt–Ni substitution on the crystal structure and magnetic behavior of the PrNi x Pt1−x compounds. Polycrystalline samples with x =1, 0.9, 0.75, 0 were prepared and characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). The analysis of XRPD data confirmed that the orthorhombic CrB-type structure owned by the parent binary compounds remains conserved through the entire series. The samples were subsequently investigated by specific heat (C p ), magnetization (M) and ac susceptibility measurements in the temperature range 2–350K and in magnetic fields up to 9T. All compounds were found to order ferromagnetically. The T C values monotonously increase with increasing Ni content. To inspect the crystal-field (CEF) effects and magnetocaloric properties specific-heat data were analyzed in detail and the magnetic contribution to the specific heat together with the magnetic entropy have been determined. The results of first principles electronic structure calculations of the PrNi and PrPt confirmed that besides the stable Pr magnetic moments due to localized 4f-electrons only a very small magnetic moments of at most 0.2μ B is induced at the Ni (Pt) site due to the polarized 3d-electron states (5d-electron states) hybridizing with the Pr 5d-electron states, i.e. the Ni (Pt) moment plays only minor role in the total balance of the magnetic moments in these compounds. [Copyright &y& Elsevier]

Abstract: A first-principle theory of spontaneous volume magnetostriction is presented. It is based on self-consistent electronic structure calculations for a magnetically ordered ground state and a disordered local moment state. The effect of highly localized 4f orbitals of rare-earth (R) atoms is taken into account by an open-core treatment within the local spin-density approximation. The theory is applied to hexagonal gadolinium and to selected intermetallic compounds with the cubic C15 Laves structure: RCo2 (R=Gd,Dy,Er) and GdAl2. The results are compared to those of experiment and discussed in terms of: (i) magnitudes of the local moments and (ii) volume-dependent exchange interactions. [Copyright &y& Elsevier]