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Now showing items 1 - 16 of 55

  • Housing and Health in West Belfast: A Case Study of Divis Flats and the Twinbrook Estateby T. Blackman; E. Evason; M. Melaugh; R. Woods

    Review by: Julian Little  

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  • Z. Holzbfecher, L. Divis, M. Kral, L. Sucha and F. Vlacil, Handbook of Organic Reagents in Inorganic Chemistry : Ellis Horwood, Chichester, (J. Wiley, Halsted Press), 734 pp., price £19.00 ($ 41.80).

    W.I. Stephen  

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  • Handbook of organic reagents in inorganic analysis: By Z. Holzbecher, L. Divis, M. Kral, L. Sucha, and F. Vlacil. Pp. 734. Published by Ellis Horwood Ltd., Distributed by John Wiley & Sons Ltd., Chichester. 1976. £19.00; $41.80

    R. Belcher  

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  • Magnetism and magnetocrystalline anisotropy of Np 2T 2X (T=Co, Ni, Ru, Rh, Pd, Ir, Pt; X=In, Sn) compounds derived from density functional calculations

    Divis, M.   Richter, M.   Eschrig, H.  

    Ab initio electronic structure calculations for Np 2T 2X intermetallic compounds were performed using an optimized linear combination of atomic orbitals method based on the local density approximation. Thus, we are aiming at a theoretical description of magnetic properties in the normal metallic state. The 5f-states of Np were assumed itinerant and treated as band states. The particular composition dependent electronic structure results from the interplay between two main ingredients: first, the band filling of the free electron background (s-, p- and neptunium d-electrons) and the transition metal bonding bands, and second, covalency (hybridization) between bonding predominantly d-states of T atoms and antibonding predominantly f-states of Np atoms. Spin and orbital moments were obtained from fully relativistic spin-polarised calculations. A quantitative study of the magnetocrystalline anisotropy is provided on the basis of calculated differences of eigenvalue sums for different orientations of the magnetic moment. We show that the results of our approach agree with the observed experimental trends in the magnetic properties of Np 2T 2X
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  • Electronic structure and magnetism of UCoGe from first principles

    Divis, M.  

    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. Gorlach, H.v. Lohneysen, 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 0.1 mu(B)) as a result of almost complete cancellation between the spin magnetic moment of 1.2 mu(B) and the opposite orbital magnetic moment of 1.1 mu(B), resulting from strong spin-orbit coupling at the uranium site. A magnetic moment of 0.4 and 0.2 mu(B) was found at the cobalt site using the APW + lo and the FPLO method, respectively. (C) 2008 Elsevier B.V. All rights reserved.
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  • Structural and electronic properties of YPd(5)Al(2)

    Divis, M.   Cermak, P.   Javorsky, P.  

    We present a study of structural and electronic properties of YPd(5)Al(2). Specific-heat measurements reveal a relatively low Sommerfeld coefficient of the electronic contribution gamma=4.1 mj mol(-1) K(-2). No superconductivity is found down to 0.4 K. First-principles electronic-structure calculations based on density-functional theory have been performed and have been compared with available experimental structural and electronic data. (C) 2011 Elsevier B.V. All rights reserved.
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  • Handbook of organic reagents in inorganic analysis: By Z. Holzbecher, L. Divis, M. Kral, L. Sucha, and F. Vlacil. Pp. 734. Published by Ellis Horwood Ltd., Distributed by John Wiley & Sons Ltd., Chichester. 1976. £19.00; $41.80

    R. Belcher  

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  • A new combined quantum simulation approach for nanomagnets

    Liu, Z. -S.   Sechovsky, V.   Divis, M.  

    We have developed a new quantum Monte Carlo approach and utilized it to calculate the magnetic structure, magnetization, and specific heat, etc., of nanoparticles composed of 3d magnetic ions. For comparison, we also performed simulations with the self-consistent computational algorithm which we proposed recently. The calculated results obtained with the two methods are identical, verifying their correctness. We also found that the combination of the two above algorithms can improve the computational efficiency considerably and have more general applicability. (C) 2012 Elsevier B.V. All rights reserved.
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  • Magnetic properties of PrRhIn(5)-Experimental study and ab initio calculations

    Uhlirova, K.   Divis, M.   Sechovsky, V.  

    The magnetization (magnetic susceptibility), specific heat and electrical resistivity of a PrRhIn(5) single crystal were studied. Van Vleck-type paramagnetic behavior and strong magnetocrystalline anisotropy were observed, which is attributed to a strong crystal-field effect on the Pr(3+) ion. A crystal-field effect on the electrical resistivity was observed as well. We focused on the measurement of the specific heat down to low temperatures (down to 0.4 K) in different magnetic fields. Indications of a field-induced transition to the quadrupolar ordered state below 0.4 K were found in the specific-heat data in magnetic fields. First-principles calculations based on density functional theory of the electronic structure and crystal-field interaction were performed in order to better understand the experimental findings. (C) 2008 Elsevier B.V. All rights reserved.
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  • Magnetism in REPdSn (RE = La, Pr, Nd) compounds: A single-crystal study

    Mihalik, M.   Divis, M.   Kitazawa, H.   Sechovsky, V.  

    The lack of data obtained on single crystals of the REPdSn intermetallic compounds (RE = La, Pr, Nd) motivated us to grow single crystals of these compounds and to study intrinsic magnetic and related electronic and thermal properties of these materials with an emphasis on magnetocrystalline anisotropy. All the three compounds crystallize in the orthorhombic TiNiSi-type crystal structure. The results of specific heat, magnetization and resistivity measurements have revealed that LaPdSn is a paramagnet at temperatures down to 2 K, PrPdSn and NdPdSn order antiferromagnetically below T(N) = 4.2(1) and 3.4(1) K, respectively, and exhibit considerable magnetocrystalline anisotropy. The latter compound undergoes an order-to-order phase transition at 1.9(3) K. At sufficiently high temperatures the susceptibility of the Pr- and Nd-compounds follows a Curie-Weiss law with the effective magnetic moment almost identical in all the three principal crystallographic directions to the value expected for the corresponding free RE(3+) ion. The values of the paramagnetic Curie temperature manifest the anisotropy of the susceptibility in paramagnetic state, which is particularly pronounced for PrPdSn. As temperature decreases the susceptibility exhibits anisotropic departure from the Curie-Weiss behavior as a consequence of the crystal field (CF) influence on the RE ions. The involvement of the crystal field in the magnetism of the RE ions is also reflected in the Schottky contribution to the specific heat which reflects the splitting of the CF energy levels and the reduced values of the RE ordered magnetic moments due to the unpopulated higher-energy CF energy levels at low temperatures. Interesting features of magnetism in PrPdSn and NdPdSn are reflected also in the electrical resistivity and magnetoresistivity. For closer understanding of magnetism in the studied REPdSn compounds we have also performed first principles electronic structure calculations. We present the calculated density of states (DOS) of REPdSn compounds and we also compare the obtained experimental results with the theoretical predictions from the calculated electronic structure. (C) 2008 Elsevier B.V. All rights reserved.
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  • Specific heat study of R2RhIn8 (R=Y, La, Lu) compounds

    Cermak, P.   Divis, M.   Kratochvilova, M.   Javorsky, P.  

    We present a detailed specific heat analysis of the non-magnetic R2RhIn8 (R=Y, La, Lu) compounds, crystallizing in the tetragonal Ho2CoGa8-type structure. We focus on the lattice contribution and analyze the characteristic parameters in the Debye and Einstein models. The most prominent feature is the presence of low energy phonons in these compounds. We also give details about the single crystal preparation and structural parameters. First-principles electronic-structure calculations based on density-functional theory have been performed and compared with available experimental structural and electronic data. (C) 2013 Elsevier Ltd. All rights reserved.
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  • A RELA=C3=87=C3=83O COMO OPERADOR M=C3=81GICO. SUPERANDO A DIVIS=C3=83O ENTRE SOCIOLOGIA PROCESSUAL E RELACIONAL

    Vandenberghe, Fr=C3=A9d=C3=A9ric  

    Abstract Relational sociology is not a paradigm, but a thematic cluster of theories that take the relation as their central category. Within the cluster, there are, basically, two approaches, a relational-structural one and a processual-interactionist one, that fly under the same flag but are in tension with each other. The task of general relational theory is to unify these two approaches, though nothing indicates that such a unified theory is at hand. In this chapter, I do some initial mapping of the field. I propose Karl Marx, Georg Simmel, Gabriel Tarde and Marcel Mauss as prime relational theorists and suggest that, together, they form a system. Similarly, I distinguish four relational constellations and argue that a relational social theory needs to systematically interweave structuralism, processualism, interactionism and symbolism into a general theory that articulates structure, culture and practices.=09
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  • Low-temperature properties of pyrochlore Lu2Ir2O7

    Klicpera, M.   Vlaskova, K.   Divis, M.  

    Low-temperature properties of Lu2Ir2O7 were studied by means of magnetization, ac-susceptibility and specific heat measurements. Our low-temperature measurements reveal a bifurcation of ZFC and FC magnetization data below 140 K, which is further pronounced as a broad anomaly in the temperature development of specific heat and ac-susceptibility. The anomaly can be attributed to the same physical mechanism as discussed for other A(2)Ir(2)O(7) with A =3D magnetic rare-earth element, i.e. to short-range correlations among Ir-4(+) magnetic moments, rather than to a long-range order of Ir sublattice reported earlier. The ac-susceptibility data revealed a strong frequency dependence of the signal, a paradigmatic sign of a spin-glass transition. The analysis of low-temperature specific heat data brought important information on physical properties of Lu2Ir2O7, in striking agreement with our density functional theoretical (DFT) calculations, concluding relatively weak electron-phonon interaction and semimetallic ground state in Lu2Ir2O7.
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  • Ab initio calculations of crystal field in MAl 2 (M=La,Y,Sc) Laves phases

    Divis, M.   Kuriplach, J.   Novak, P.  

    The crystal field (CF) parameters of trivalent rare-earth impurities in the intermetallics MAl 2 are determined by integrating the products of the aspherical components of the crystal potential and the radial density of the 4f electrons. The potential results from the self-consistent calculation of the electronic structure of MAl 2 using the FLAPW method in the LDA approximation. The calculated values of the CF parameter A 40 follow the sequence found in the experimental data
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  • First-principles calculation of crystal field parameters of Dy ions substituted for Nd in Nd-Fe-B magnets

    Tanaka, S.   Moriya, H.   Tsuchiura, H.   Sakuma, A.   Divis, M.   Novak, P.  

    We study the electronic structures of crystalline Nd2Fe14B, Dy2Fe14B and Dy-doped Nd-Fe-B, and estimate the crystal field parameter A(2)(0)< r(2)> of the rare earth ions of these systems based on the first principles calculations. We find that the crystal field of the Dy ions is appreciably insensitive to its crystallographic location than that of Nd ions.
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  • Specific heat study of Tm xY 1-xCu 2

    Javorsky, P.   Divis, M.   Sima, V.   Bischof, J.  

    The specific heat of Tm xY 1-xCu 2 ( x=0.1,0.2,0.3,0.4,0.6 and 0.8) has been measured at temperatures up to 30 K. The antiferromagnetic ordering has been observed for x=0.6 and 0.8. The singlet ground state antiferromagnetism is discussed in terms of the molecular field approximation applied on the two lowest levels (quasidoublet). This crystal field ground state quasidoublet and its separation from higher states has been studied by means of the specific heat data analysis
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