Browsing by Author "Fisk, Zachary"

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    Influence of magnetic order on optical properties of the heavy-electron antiferromagnets
    (1994) Degiorgi, Leonardo; Ott, Hans Rudolf; Grüner, George; Dressel, Martin; Fisk, Zachary
    We discuss the influence of antiferromagnetic order on optical properties of several heavy-electron systems. We find different electrodynamic responses of local magnetic moment and itinerant heavy-electron antiferromagnets.
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    Optical evidence of Anderson-Mott localization in FeSi
    (1994) Degiorgi, Leonardo; Hunt, M. B.; Ott, Hans Rudolf; Dressel, Martin; Feenstra, Bokke Johannes; Grüner, George; Fisk, Zachary; Canfield, P.
    We have investigated the electrodynamic response of single-crystalline FeSi over a frequency range from d.c. to 10 hoch 5 cm-1. At low frequencies, we found evidence for an Anderson-Mott localization behaviour of the low-temperature optical conductivity, while at high frequencies the excitation spectrum resembles that of a conventional semiconductor. The missing spectral weight below the gap energy is redistributed around the gap edge, in disagreement with previous claims based on optical measurements.
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    Optical probing of the antiferromagnetic phase transition in the heavy-electron compounds U2Zn17 and UCu5
    (1994) Degiorgi, Leonardo; Ott, Hans Rudolf; Dressel, Martin; Grüner, George; Fisk, Zachary
    We have investigated the complete electrodynamic response of the heavy-electron compounds U2Zn17 and UCu5. Particular emphasis has been devoted to the optical evidence of the antiferromagnetic phase transitions at 9.7 K and 15 K for U2Zn17 and UCu5, respectively. In UCu5, we found an absorption in the far infrared, which is ascribed to excitations across a spin-density-wave-type gap. This feature is absent in U2Zn17. We argue that UCu5 belongs to a characteristically different class of antiferromagnets than U2Zn17 which represents the class of heavy-electron compounds with localized magnetic moments.