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  • 1990-1994  (14)
  • 1
    Electronic Resource
    Electronic Resource
    Magnetism and bonding in light actinide and rare earth systems (invited) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5897-5902 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The importance of including all of Hund's rules in self-consistent electronic-structure calculations in solids is pointed out. We present a scheme that accounts for the interactions that lead to these rules, and we give examples of when these interactions become important. Calculated ground state properties (chemical bonding, magnetic moment, magnetic form factor) of actinide and rare earth systems are found to agree better with experiment when all Hund's rules are accounted for. On the other hand, but also in agreement with experiment, we find that Hund's second and third rule contributions for Fe, Co, and Ni are small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347865
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Calculated magnetic moments of Nd2Fe14B : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5708-5710 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent spin-polarized band-structure calculation has been performed for the technically important permanent magnet compound Nd2Fe14B. In contrast to earlier calculations, the localized 4f states on the Nd sites are treated in a consistent way. They are not allowed to contribute to the bonding, but they produce a local exchange field, felt by the valence electrons, which is calculated from first-principles local density theory. Assuming a Russel–Saunders coupled Nd 4f moment of 3.3μB/atom, the total magnetic moment is calculated to be 38.1μB/formula unit, to be compared with the experimental value 37.1μB/formula unit [Givord, Li, and Perrier de la Bathie, Solid State Commun. 51, 857 (1984)]. The calculated local Fe moments are quite different on the different crystallographic sites, varying from 2.1μB to 2.9μB/atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347895
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of anisotropy constant in US with polarized neutrons (invited) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4803-4806 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Uranium compounds can have an anisotropy that is considerably greater than that found in rare-earth compounds. Early estimates of K1 in ferromagnetic US (Tc = 178 K), for example, were that K1 (approximately-greater-than) 108 erg/cm3. We have re-examined this cubic material and determined K1 in the range of reduced moment (μ/μ0) from 0.1 〈 (μ/μ0) 〈 0.7 and find that it varies logarithmically over almost three orders of magnitude. The highest measured K1 is 2 × 108 erg/cm3 at (μ/μ0) = 0.7, but an extrapolation, which we anticipate on arguments of symmetry, to (μ/μ0)=1, (T=0 K) gives K1 ∼ 1010 erg/cm3, some 20 times more than found in TbFe2 at 0 K. The method we have used is with polarized neutrons. Because the neutron interaction with the magnetic moment is vectorial in nature we can determine individually the magnitude and direction of the moment in an applied field. In many cases this method has advantages over conventional methods, especially when the anisotropy is large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348236
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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
    A study of Ni-Ge interdiffusion on GaAs using rapid thermal annealing with temperature standards (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1641-1648 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new technique for probing rapid material interactions at low temperatures has been developed. Rapid thermal annealing at 200 and 250 °C is exploited as a temperature-time probe to study the fast kinetics of Ni-Ge and Ni-Ge-Au contact metallizations on GaAs. Temperature standards are employed to establish known reaction temperatures within −3 to +13 °C of nominal, while anneal times are limited to 30 s or less. Rutherford backscattering analysis of annealed samples indicate that Ge consumption obeys parabolic kinetics, most likely limited by Ni diffusion, consistent with the growth of a NixGe phase. An activation energy estimate ≈0.7 eV is shown to be consistent with the fast interdiffusion observed, which is attributed to a grain boundary mechanism. The presence of Au plays only a limited role in the reaction for the temperatures and times studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346645
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  • 10
    Electronic Resource
    Electronic Resource
    Electronic structure and the Stoner I parameter for RPd3 compounds (R=La, Ce, Pr, and Nd) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6298-6300 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gardner et al. have made measurements of the magnetic susceptibility in a large range of temperature for a complete series of RPd3 compounds (R=rare earths). Some band structure calculations exist on LaPd3 and CePd3. However, the question of magnetic ordering has not been addressed in existing theoretical work. With a view to understand the magnetic behavior of these compounds we have performed self-consistent band structure calculations for LaPd3, CePd3, PrPd3, and NdPd3. Our calculations predict magnetic ordering only in PrPd3 and NdPd3 and hence are consistent with the experimental findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355378
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