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  • 1
    Electronic Resource
    Electronic Resource
    Enhancement of orbital magnetism at surfaces: Co on Cu(100) (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4983-4983 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By combining MCXD experiments with first principles electronic structure calculations, we demonstrate that the orbital contribution to magnetism can be strongly enhanced at surfaces. This effect is illustrated for Co grown on a Cu(100) surface. The MCXD measurements were performed using the SX 700 plane grating monochromators at BESSY. The Co films were evaporated and characterized in situ, for their cleanness, thickness (1.6–50 ML), and structural order. For a film thickness up to 2.2 ML, measurements of the ac MCXD susceptibility response at a fixed photon energy allowed one to measure the critical temperature, Tc, of the films and their critical properties were characterized in situ. For several samples the MCXD response as a function of the x-ray incidence angle was investigated as well. This allows one to quantify and correct saturation effects that can occur in the measurements. Data were taken in a temperature range between 40 and 350 K, and for many samples measurements were performed at several reduced temperatures, T/Tc. The first layer of Co on the Cu(100) surface shows an enhanced orbital moment, in contrast to the subsequent layers where the orbital moment is bulklike. The lowering of the symmetry, the enhanced spin moment, and the increased value of the density of states at the Fermi level are factors that combine to give the observed enhancements. © 1996 American Institute of Physics. [S0021-8979(96)679608-0]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361611
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  • 2
    Electronic Resource
    Electronic Resource
    On the γ-like surface of α-Ce: Theory (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5837-5837 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have shown theoretically, by means of a full-potential LMTO method in a slab geometry, that the topmost surface layer of α-Ce is γ-like. The calculations are fully relativistic and include all electrons. Also an orbital correction to the f-electron states is included to allow for f localization. For the topmost layer the spin moment is found to be 0.70 μB for the f electrons and 0.08 μB for the d-electron states while the orbital moment from the f electrons is found to be −1.07 μB. These moments correspond well to the moments calculated for bulk γ-Ce which are 0.63, 0.07, and −0.87 μB, respectively. The subsurface and lower lying layers are calculated to have spin and orbital moments close to zero. We therefore conclude that the topmost layer on the α-Ce surface is γ-like while the subsurface and lower lying layers are similar to bulk α-Ce. Our findings explain recent photoemission experiments on this material and provide a theoretical foundation for the interpretation of these experiments. The fact that our theory assumes that α-Ce has delocalized f electrons, and the agreement with the interpretation of photoemission experiments, gives support that the Mott transition model for the α→γ phase transition is correct. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362203
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  • 3
    Electronic Resource
    Electronic Resource
    Reactively magnetron sputtered Hf-N films. I. Composition and structure (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3104-3111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of Hf-N, covering the entire composition range from pure Hf to overstoichiometric HfN, have been prepared by reactive magnetron sputtering. The structure of the films has been investigated by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy and the composition has been determined using Auger electron spectroscopy. A solubility of ≈30 at. % nitrogen is found in the α-Hf region. Above 30 at. % N a multiphase structure consisting of α-Hf, HfN, Hf3N2, and/or Hf4N3 is found, which is not in agreement with the equilibrium structure. In the mononitride region a lattice parameter of ≈4.53 A(ring) is observed. This value is slightly higher than reported bulk values due to intrinsic stress in the films. Increasing the nitrogen content above 50 at. % causes a distortion of the cubic symmetry of the lattice. This is first observed as an increase in the (111) interplanar spacing while other spacings decrease. Also a splitting of some reflections occurs at higher nitrogen contents. This phase transition is suggested to be due to a successive change from a cubic to a rhombohedral structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335812
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  • 4
    Electronic Resource
    Electronic Resource
    Calculated ground-state properties of ternary uranium compounds : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6580-6582 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The compounds UTAl (T=Fe,Co,Ni,Ru,Rh,Ir,Pt) crystallize in the hexagonal ZrNiAl structure. Measurements suggest that the 5f electrons in these compounds are itinerant [V. Sechovsky and L. Havela, in Ferromagnetic Materials, edited by E. P. Wohlfarth and K. H. J. Buschow (North-Holland, Amsterdam, 1988), Vol. 4, p. 309]. From self-consistent linear muffin-tin orbital energy-band calculations for the compounds the transition to magnetism across the series is explained in terms of the calculated Stoner products. Inclusion of spin-orbit interaction leads to an induced orbital moment in URhAl, consistent with the experimental observation that the magnetic properties of these compounds are highly anisotropic [V. Sechovsky and L. Havela, in Ferromagnetic Materials, edited by E. P. Wohlfarth and K. H. J. Buschow (North-Holland, Amsterdam, 1988), Vol. 4, p. 309].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349863
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  • 5
    Electronic Resource
    Electronic Resource
    Metamagnetism of RCo2 compounds : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6583-6585 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-consistent spin-polarized energy-band calculations are reported for the RCo2 compounds (R=Tb–Yb). By changing the magnitude of the 4f spin in GdCo2 from zero to seven and back to zero, hysteresis was obtained with both low- and high-moment conduction-electron states being obtained for spin less than 4. For the real compounds, when the calculations were started with no moment on the Co, low-conduction-electron moments were obtained for DyCo2–YbCo2. However, when the calculations were started with large moments on the Co the total conduction-electron moments were calculated to be 1.75 μB/f.u. for all of the compounds. It is suggested that the conduction-electron-state densities in all of the compounds are similar to those in YCo2 and LuCo2 and that the conduction-band system is essentially metamagnetic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349864
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  • 6
    Electronic Resource
    Electronic Resource
    Calculated spin and orbital moments in UNi2 : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6586-6587 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For the hexagonal ferromagnet UNi2, an unusual 5f form factor for uranium has been observed, indicating a large orbital contribution to the total moment. We report on self-consistent electronic structure calculations for the hexagonal Laves phase (C14) compound UNi2, taking both spin and orbital contributions to the total moment into account. In a constrained calculation, where the spin moment is chosen to agree with experiment, very good agreement with the experimental form factor is obtained. In the analysis of the form factor both the 6d and the 5f electrons are taken into account giving improved agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349865
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio calculation of molecular field interactions in rare-earth transition-metal intermetallics (invited) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5972-5976 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction, KRM, between the rare-earth 4f moment and the transition-metal 3d moments in rare-earth transition-metal intermetallics is shown to depend upon the R-5d moment, which is due to 3d–5d hybridization, and local 4f–5d exchange integrals. Both the R-5d moment and KRM may be calculated ab initio from the local spin-density approximation to density functional theory in self-consistent energy-band calculations with the localized 4f-moments fixed at their Russel–Saunders values. Detailed examples are given for the RFe2 (R=Gd−Yb) series. The exchange integrals are similar to those entering into the density functional version of Stoner theory and their energy dependence must be treated carefully. The calculated local exchange integrals are shown to be related to the molecular fields derived from spin Hamiltonians, hence to the spin-wave spectra. Reasonable agreement with values of the molecular fields extracted from inelastic neutron scattering and high field susceptibility measurements is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350092
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetism of RFe2 compounds : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5683-5684 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The combination of itinerant transition metal (M=Fe) and localized rare earth (R=Gd-Yb) magnetism in RFe2 compounds has been investigated in self-consistent energy band calculations. The computed and measured total moments are in good agreement. We find, however, that there is a significant contribution to the moment from the R-5d partial moments coupled antiparallel to the Fe-3d moment which results from 3d-5d hybridization. The R-4f moments interact with the conduction band system solely by local exchange interactions which are calculated ab initio from density functional theory. A sum rule for the total 3d+5d moment is shown to be obeyed and an expression for the effective ferrimagnetic exchange interaction between 3d and 4f electrons is derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347937
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  • 9
    Electronic Resource
    Electronic Resource
    Density functional theory for calculation of elastic properties of orthorhombic crystals: Application to TiSi2 (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4891-4904 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young's modulus, and Poisson's ratio for ideal polycrystalline TiSi2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young's modulus for single crystal TiSi2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the experimental results. The shear anisotropic factors and anisotropy in the linear bulk modulus are obtained from the single crystal elastic constants. From the site and angular momentum decomposed density of states combined with a charge density analysis and the elastic anisotropies, the chemical bonding nature between the constituents in TiSi2 is analyzed. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. The calculated elastic properties are found to be in good agreement with experimental values when the generalized gradient approximation is used for the exchange and correlation potential. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368733
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  • 10
    Electronic Resource
    Electronic Resource
    Reactively magnetron sputtered Hf-N films. II. Hardness and electrical resistivity (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3112-3117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microhardness and electrical resistivity have been measured on thin Hf-N films, covering the entire composition range from pure Hf to overstoichiometric HfN. Influence of substrate bias on the properties of stoichiometric HfN films has also been studied. All films have been prepared by high-rate reactive magnetron sputtering at a substrate temperature of 400 °C. Both hardness and resistivity increase as nitrogen is added to the α-Hf phase. For the cubic HfN phase the hardness has a maximum, ≈3500 HV, and the resistivity a minimum, 225 μΩ cm, at a composition close to stoichiometry. However, both values are considerably higher than those reported for bulk samples. This is explained in terms of nonequilibrium growth conditions, giving rise to high densities of dislocations and interstitially incorporated nitrogen atoms. For films with a nitrogen content above 50 at. % a very high-resistivity value is found, 2.0 Ω cm at maximum. By applying a low substrate bias voltage the resistivity of stoichiometric HfN was decreased with a factor of about 3, and simultaneously a grain growth and/or reduced defect concentration was observed. At higher bias voltages the resistivity increases and the grain sizes decrease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335813
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