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  • 1
    Electronic Resource
    Electronic Resource
    Optical response of Cu3Ge thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8115-8117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report an investigation on the optical properties of Cu3Ge thin films displaying very high conductivity, with thickness ranging from 200 to 2000 A(ring), deposited on Ge substrates. Reflectance, transmittance, and ellipsometric spectroscopy measurements were performed at room temperature in the 0.01–6.0, 0.01–0.6, and 1.4–5.0 eV energy range, respectively. The complex dielectric function, the optical conductivity, the energy-loss function, and the effective charge density were obtained over the whole spectral range. The low-energy free-carrier response was well fitted by using the classical Drude–Lorentz dielectric function. A simple two-band model allowed the resulting optical parameters to be interpreted coherently with those previously obtained from transport measurements, hence yielding the densities and the effective masses of electrons and holes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362370
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical interpretation of optical conductivity of YbCu4Ag,Au : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6423-6425 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We focus on YbCu4Ag and YbCu4Au and interpret the optical conductivity, measured from 2 meV to 6 eV at 10 and 300 K, in terms of self-consistent electronic structure calculations. Most of the relevant spectral structures are interpreted as interband transitions from hybridized f–d states below and at the Fermi level at high symmetry points. In particular, the large shoulder at about 2.4 and 2 eV in the spectrum of YbCu4Au and YbCu4Ag, respectively, can be interpreted in terms of a transition Γ4→Γ3 involving mostly d states. We also compare the electronic structure of YbCu4Ag with that of LuCu4Ag, to ascertain the influence of the f states on the conduction bands and carrier density at EF. This allows us to draw some qualitative considerations on the f-band hybridization in these compounds. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361958
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  • 3
    Electronic Resource
    Electronic Resource
    Narrow bands and magnetic properties of heavy fermions (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3422-3422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Far infrared measurements performed at low temperature on the heavy fermions UPt3 and CeCu6 give us evidence that an appropriate model describing these materials must consider two narrow quasiparticle bands in the vicinity of the Fermi level separated by a gap, or a pseudogap, in the order of a few meV. The bandwidth obtained by point contact spectroscopy is also in the meV range. With such a model and with the experimentally obtained values for the bandwidth and the gap we tried to calculated the temperature dependence of the resistivity and of the γ value of the specific heat and we found a very good agreement with the experiments. We want now to apply the model to calculate the magnetic properties of the heavy fermions. We show that a Pauli susceptibility including the effects of a strongly energy dependent density of states can account for the temperature dependence of the susceptibility in these materials. For temperatures above about 50 K we find a Curie law and for lower temperatures we compute a weak maximum. Furthermore, the magnetic saturation of UPt3 in very large fields (35 T) can be explained in this context as a splitting of the quasiparticle band at the Fermi level in two completely separated spin polarized subbands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340754
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  • 4
    Electronic Resource
    Electronic Resource
    Optical study of the temperature-induced valence transition in YbCu4In : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5418-5420 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the context of investigations on mixed valence and Kondo systems the compound YbCu4In is interesting due to a temperature-induced valence transition occurring at Tv=40 K. Without distorsion in the C156 crystal structure, the Yb state in the system changes from a nearly 2+ state below Tv to a magnetic (3+) state above Tv. We investigated the effects of such a change on the optical reflectivity which has been measured over a large spectral range (1 meV–6 eV) and at different temperatures above and below Tv, both on a polycrystalline sample of YbCu4In, and on a similar sample of the reference compound LuCu4In. A detailed analysis of the spectra in the far infrared is complicated by the presence both in Yb and Lu-based compounds of an optical structure at about 5 meV, which could be due to a phonon mode. Regardless, some differences in the spectra and changes in the plasma frequency have been observed, allowing for considerations on the connections between the valence of Yb and the density and effective mass of the carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353701
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  • 5
    Electronic Resource
    Electronic Resource
    Optical constants and electrical transport parameters of HfSi2 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7645-7650 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HfSi2 polycrystalline thin films, grown by coevaporation of Hf and Si and subsequently annealed at 850 °C, were studied by electrical resistivity measurements (from 10 to 900 K), Hall voltage (from 10 to 300 K), and optical reflectance (at room temperature) from 5 meV to 12 eV. Composition and structure of the films were investigated by Rutherford backscattering spectroscopy and x-ray diffraction. HfSi2 is metallic with (i) a high residual resistivity, (ii) a phonon contribution to the resistivity showing a negative deviation from linearity, and (iii) low-energy interband transitions. Transport measurements yielded a Debye temperature of 430 K, a free-carrier concentration of ∼4×1021 cm−3, and a mean free path of 139 A(ring). The reflectivity was Kramers–Kronig transformed to obtain the dielectric functions which, at low energies, are discussed in term of the Drude model. The optical parameters agree quite well with transport results, thus permitting one to obtain a reasonable value for the Fermi velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347535
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic structure and magnetic properties of URhSi : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6438-6440 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Orthorhombic URhSi orders ferromagnetically below Tc=9.5 K, with an ordered magnetic moment μ=0.11μB per U atom and has a relatively enhanced value of the specific heat cp/T=186 mJ/mol K2. U-U atomic distances fall in a critical region around the Hill limit so that it is thought to be an itinerant magnet. Our present investigation includes: (i) preparation of high purity crystalline samples further analyzed by single crystal x-ray diffraction and magnetization measurements; (ii) band structure calculations performed with self-consistent full potential linearized Augmented plane wave method within the local density approximation; (iii) optical measurements at room and at low temperature over a large spectral range (2 meV–6 eV). As a result, the details of the crystal structure of URhSi have been refined with respect to previous measurements on powdered samples. The comparison of electronic structure calculations and optical results show: (a) a low mobility of free carriers and a large dielectric screening at the lowest frequencies, connected with excitation of f states hybridized with d states at the Fermi level; (b) smooth spectral features due to the huge number and density of states (the main contribution being due to occupied Rh d states). The whole amount of information obtained would suggest the presence of Kondo-like behavior in this compound, independently on the magnetic order. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367777
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  • 7
    Electronic Resource
    Electronic Resource
    Optical and electrical characterization of VSi"2 and NbSi"2 single crystals
    Amsterdam : Elsevier
    Applied Surface Science 73 (1993), S. 237-242 
    Details
    ISSN: 0169-4332
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0169-4332(93)90172-8
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic structure of UPt"3: A low energy optical study
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 63-64 (1987), S. 377-379 
    Details
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-8853(87)90613-5
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  • 9
    Electronic Resource
    Electronic Resource
    Narrow bands and magnetic properties of heavy fermions
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 73 (1988), S. 229-232 
    Details
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-8853(88)90298-3
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  • 10
    Electronic Resource
    Electronic Resource
    Electronic structure and magnetic properties of heavy fermions
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 70 (1987), S. 364-368 
    Details
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-8853(87)90468-9
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