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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6301-6302 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Dhar et al. [J. Phys. F 18, L41 (1988); and Proceedings of the International Conference on Strongly Correlated Electron Systems Sendai, Japan, 1992 (Plenum, New York, 1987)] have recently measured the low-temperature specific heat of YbSbPd and YbSbNi. Their measurements yield large values for the specific heat coefficient (1384 states/Ry cell for YbSbPd and 865 states/Ry cell for YbSbNi), and suggest a magnetic transition at low temperature. With a view to understand the ground state of these compounds, we have performed self-consistent scalar relativistic linear muffin-tin orbital band structure calculations. Our paramagnetic calculations for YbSbPd and YbSbNi give the density of the states at Fermi level to be 82.94 and 27.96 states/Ry cell, respectively. These give enhancement factors of 16.7 and 30.1 for YbSbPd and YbSbNi. We present results of our calculations of the band structure as well as the Stoner I parameter for these compounds.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6298-6300 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6580-6582 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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].
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6583-6585 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6586-6587 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4803-4806 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5897-5902 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5683-5684 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5708-5710 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
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