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Bauer, E., R. Hauser, A. Galatanu, A. Lindbaum, G. Hilscher, H. Sassik, H. Kirchmayr, J. G. Sereni, and P. Rogl. "New phase boundary between magnetic and non-Fermi-liquid in Ce(Rh1-xRux)(3)B-2, for 0 <= x <= 0.4." Journal of Applied Physics 83, no. 11 (1998): 6423–6425.
Abstract: A study of the temperature-dependent magnetic susceptibility and electrical resistivity rho(T) (0.5-300 K) on single-phase alloys (CaCu5 type), prepared by argon are melting, reveals a magnetic phase transition with a nonmonotonous decrease of the ordering temperature from T-c = 115 K for x = 0 to T-c approximate to 0 for x = 0.40. A kink in the susceptibility at about 70 K indicates that ferromagnetism (at x < 0.1) transforms to a complex magnetic order for 0.125 less than or equal to x less than or equal to 0.35. Above that concentration rho(T) = rho(0) + AT(n) changes from n approximate to 2 to n approximate to 1.5, a characteristic for non-Fermi-liquid behavior. Under pressure T-c stays almost constant for x = 0.125 but dT(c)/dp grows with increasing Ru content. On the contrary, applied fields up to 12 T do not affect T-c. Low-temperature specific heat and ac susceptibility for x = 0.40 confirm the absence of long-range magnetic order down to 0.5 K, For x = 0.35 C-p/T = 62 mJ/mol K at 1.5 K, a value which is three times larger than that of CeRh3B2. (C) 1998 American Insitute of Physics. [S0021-8979(98)46511-3].
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Berisso, M. G., O. Trovarelli, P. Pedrazzini, G. Zwicknagl, C. Geibel, F. Steglich, and J. G. Sereni. "Nonmonotonous evolution of the Kondo temperature in the phase diagram of Ce(Pd1-xCux)(2)Si-2." Physical Review B – Condensed Matter and Materials Physics 58, no. 1 (1998): 314–321.
Abstract: The evolution of the behavior of the Ce 4f electron with the Cu content in the alloy Ce(Pd1-xCux)(2)Si-2 was investigated by determining its structural, magnetic, transport, and thermal properties. Results obtained on 15 samples with compositions distributed along the whole concentration range allow us to draw a magnetic phase diagram showing three distinct regions. The first region at low Cu concentrations corresponds to the antiferromagnetic-ordered regime. The fast suppression of this magnetic order between x = 0.2 and x = 0.25 suggests the presence of a critical point which separates this region from the second one at larger.x values where no magnetic order is observed. The main characteristic of this second region, which extends up to x = 0.7, is a pronounced increase of the Kondo temperature T-K, from T-K approximate to 15 K at x = 0.25 to T-K approximate to 50 K at x = 0.7. This is in contrast with the fast decrease of T-K in the region with x > 0.7. In this region a small anomaly with a ferromagnetic character is observed in the specific hear arround 4 K. The change in the evolution of T-K with x coincides with a change in the composition dependence of the c lattice parameter of the tetragonal structure, pointing to a structure-related origin of this unusual T-K(x) behavior. This nonmonotonous T-K(x) dependence is reproduced using local-density-approximation band-structure calculations, which show a maximum of the hybridization strength between conduction electrons and Ce 4f stares for intermediate Cu concentrations. Such a T-K(x) dependence which contradicts the monotonous dependence observed in all other Ce-based alloy systems is the hallmark of the Ce(Pd1-xCux)(2)Si-2 alloy, which cannot be described as a Fermi-Liquid system in the nonmagnetic region. [S0163-1829(98)02118-3].
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Ceva, H., and J. Luzuriaga. "Correlations in the sand pile model: From the log-normal distribution to self-organized criticality." Physics Letters A 250, no. 4-6 (1998): 275–280.
Abstract: We have studied the approach of the Abelian sand pile model towards the stationary, self-organized criticality state. The uncorrelated limit is shown both numerically and by a simple analysis to follow the log-normal distribution. We introduce and evaluate several correlation functions to study the correlated region.
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Decca, R. S., H. D. Drew, B. Maiorov, J. Guimpel, and E. Osquiguil. "Photoinduced superconducting nanowires in GdBa2Cu3O6.5 films." Applied Physics Letters 73, no. 1 (1998): 120–122.
Abstract: We report the fabrication of high-Tc superconducting wires by photodoping a GdBa2Cu3O6.5 thin film. An optical near-field probe was used to locally excite carriers in the system at room temperature. Trapping of the photogenerated electrons define a confining potential for the conducting holes in the CuO planes. Spatially resolved reflectance measurements show the photogenerated nanowires to be ?250 nm wide. Electron diffusion, before electron capture, is believed to be responsible for the observed width of the wires.
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Decca, R. S., H. D. Drew, B. Maiorov, J. Guimpel, and E. Osquiguil. "Superconducting Materials Engineered Using a Near-Field Scanning Optical Microscope." Scanning 20, no. 3 (1998).
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Decca, R. S., H. D. Drew, B. Maiorov, J. Guimpel, and E. Osquiguil. "Superconducting Materials Engineered Using a Near-Field Scanning Optical Microscope." In Scanning, 156. Vol. 20., 1998.
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Fainstein, A., P. Etchegoin, and J. Guimpel. "Raman study of photoinduced chain-fragment ordering in GdBa2Cu3Ox thin films." PHYSICAL REVIEW B 58, no. 14 (1998): 9433–9439.
Abstract: Raman scattering experiments on oxygen deficient GdBa2Cu3Ox thin films (x=6.53, 6.7, 6.8, and 6.93) as a function of photoexcitation and annealing induced oxygen disorder are presented. Raman lines, unambiguously assigned to copper and oxygen vibrations involving atoms at the end of Cu-O chains, are used as markers for the existence of short chain fragments. The dynamics of chain conjunction and fragmentation was monitored by the peak intensity dependences with photoexcitation time and annealing temperature. These results demonstrate the presence of photoassisted oxygen ordering in these high-T-c superconductors, and give definitive support for its ultimate role in the phenomena of persistent photoconductivity and photoinduced superconductivity. [S0163-1829(98)04037-5].
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Ferrari, H., S. O. Valenzuela, V. Bekeris, J. Guimpel, and F. de la Cruz. "Short-time magnetization in superconducting thin films." REVISTA MEXICANA DE FISICA 44 (1998): 193–195.
Abstract: We have investigated the magnetization in thin (Y;Gd)Ba2Cu3O7-delta superconducting films in the 100 μs time scale. Magnetic moment was measured with a non-conventional technique that combines the use of a pulsed magnetic field and a synchronized pulsed laser. Both virgin and magnetically cycled samples were examined and results are described within Bean's critical state model.
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Grigera, S. A., and Morr. "Bose-glass phase in twinned YBa2Cu3O7-?" Physical Review Letters 81, no. 11 (1998): 2348–2351.
Abstract: Using an extensive scaling analysis of the transport properties in twinned YBa2Cu3O7-? crystals we have experimentally found the predicted change in the universality class of the Bose-glass to liquid transition when the magnetic field is applied at small angles away from the direction of the correlated defects. The new dynamical critical exponent is s? = 1.1
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Grigera, S. A., E. Morre, E. Osquiguil, C. Balseiro, G. Nieva, and F. de la Cruz. "Bose-glass phase in twinned YBa2Cu3O7-delta." PHYSICAL REVIEW LETTERS 81, no. 11 (1998): 2348–2351.
Abstract: Using an extensive scaling analysis of the transport properties in twinned YBa2Cu3O7-delta crystals we have experimentally found the predicted change in the universality class of the Bose-glass to liquid transition when the magnetic field is applied at small angles away from the direction of the correlated defects. The new dynamical critical exponent is s' = 1.1 +/- 0.3.
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