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Non-Fermi-liquid scaling in U(Cu,Al){sub 5} compounds

Description: We report on the electronic properties of various UCu{sub x}Al{sub 5-x} compounds (2.9{le}x{le}3.5). These compounds crystallize in the hexagonal CaCu{sub 5} structure. For all compounds, we find that the low-temperature specific heat diverges logarithmitically, which may be taken as an indication of non-Fermi-liquid scaling in these materials. Also we find a large magnetic anisotropy in all compounds studied, and we show that the magnetic anisotropy should not be neglected in the analysis of other bulk properties. Though for some of UCu{sub x}Al{sub 5-x} polycrystals non-Fermi-liquid scaling is found also in the magnetic susceptibility, comparison with single-crystal results on UCu{sub 3}Al{sub 2} indicates that any temperature dependence may be due to averaging anisotropic response over all crystallographic directions.
Date: August 1, 1996
Creator: Nakotte, H.; Buschow, K.H.J.; Brueck, E. & Klaasse, J.C.P.
Partner: UNT Libraries Government Documents Department

GMR in intermetallics

Description: Typical examples of giant magnetoresistance (GMR) effects observed in intermetallic compounds at various conditions are reviewed and some comparisons with the GMR magnetic multilayer systems are shown. Possibilities of tuning material parameters desired for applications are discussed in context of present understanding of the mechanisms responsible for GMR in this class of materials. 18 refs.
Date: April 1, 1996
Creator: Sechowsky, V.; Havela, L.; Nakotte, H. & Brueck, E.
Partner: UNT Libraries Government Documents Department

Thermal properties of UPdSn and UCuSn

Description: The authors report on the specific-heat and the thermopower of UPdSn and UCuSn, both of which order antiferromagnetically at low temperatures. Both compounds show similar behavior in the specific heat, and the large magnetic-entropy changes around T{sub N} are evidence for a large degree of 5f-electron localizations. The thermopower, on the other hand, behaves very different in the two compounds. While prominent features are seen in the temperature dependence of the thermopower of UCuSn, only weak changes are observed for UPdSn. This may indicate that, for these compounds, the thermopower response is due to mechanisms other than purely magnetic ones.
Date: September 1, 1996
Creator: Kawanaka, H.; Nakotte, H.; Brueck, E.; Prokes, K.; Kim-Ngan, N.H.; Takabatake, T. et al.
Partner: UNT Libraries Government Documents Department

Localized excitations in UPdSn

Description: The authors have measured the inelastic neutron-scattering response of UPdSn at various temperatures using the HET and PHAROS spectrometers at the ISIS and MLNSC facilities, respectively. UPdSn shows some quasielastic scattering, which may be attributed to the hybridization of the 5f electrons with the conduction electrons. Furthermore, they find a clear excitation around 40meV above 40K in addition to the phonon contribution. While this excitation may be indicative of crystal fields in UPdSn, its strong temperature dependence seems to contradict a simple crystal-field picture. Below T{sub N}, the unusual temperature dependence may be attributed to magnetically-driven distortions (and subsequent changes in the local surrounding of the U ions), but there is some evidence that other additional mechanism(s) may contribute above T{sub N}. Some possible mechanisms will be discussed.
Date: November 1, 1997
Creator: Nakotte, H.; Robinson, R.A.; Swan, T.; Kelley, T.; Bull, M.; McEwen, K.A. et al.
Partner: UNT Libraries Government Documents Department

Magnetoresistance behavior of UNiGe

Description: The authors have measured the temperature dependences of the magnetoresistance of single-crystalline UNiGe for both parallel (i//B//c-axis) and perpendicular configurations (i//a-axis, B//c-axis) in magnetic fields up to 18 T. Both configurations yield similar magnetoresistance behavior, which emphasizes the strong magnetic contribution to the resistivity in all directions. Crossing magnetic-phase boundaries causes anomalies in the magnetoresistance, which allowed a completion of the previously proposed magnetic phase diagram.
Date: May 1, 1995
Creator: Nakotte, H.; Lacerda, A.; Purwanto, A.; Havela, L.; Sechovsky, V.; Prokes, K. et al.
Partner: UNT Libraries Government Documents Department

Magnetic properties of single-crystalline UCu[sub 3]Al[sub 2]

Description: UCu[sub 3]Al[sub 2] crystallizes in an ordered variant of the hexagonal CaCu[sub 5] structure. By neutron powder-diffraction, the U atoms were found to occupy the la sites, while the 2c sites are occupied by Cu atoms only and a random occupation of the 3g sites by the remaining Cu and Al is found. The magnetic susceptibility, measured on a single crystal grown by the Czochralski tri-arc technique, is found to be maximal within the hexagonal basal plane with a maximum at about 10 K. For fields applied within the basal plane, the magnetization at 4.2 K exhibits a slight S-shape starting slightly below 15 T. No such anomalies are found for fields applied along the c-axis where the magnetic response is found to be much lower. No additional magnetic peaks, which could be related with long-range antiferromagnetic ordering, were detected in the neutron powder-patterns at low temperatures.
Date: January 1, 1993
Creator: Nakotte, H.; Brueck, E.; Brabers, J.H.V.J.; Prokes, K.; de Boer, F.R. (Amsterdam Univ. (Netherlands). Van der Waals Lab.); Sechovsky, V. (Charles Univ., Prague (Czech Republic). Dept. of Metal Physics) et al.
Partner: UNT Libraries Government Documents Department