Abraham, J., M. Aglietta, C. Aguirre, D. Allard, I. Allekotte, P. Allison, C. Alvarez, J. Alvarez-Muniz, M. Ambrosio, L. Anchordoqui et al. "Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory." ASTROPARTICLE PHYSICS 27, no. 4 (2007): 244–253.
Abstract: Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the 'hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction. (c) 2006 Elsevier B.V. All rights reserved.
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Abraham, J., M. Aglietta, C. Aguirre, D. Allard, I. Allekotte, P. Allison, C. Alvarez, J. Alvarez-Muniz, M. Ambrosio, L. Anchordoqui et al. "An upper limit to the photon fraction in cosmic rays above 10(19) eV from the Pierre Auger Observatory." ASTROPARTICLE PHYSICS 27, no. 2-3 (2007): 155–168.
Abstract: An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 10(19) eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample support the conclusion that a photon origin of the observed events is not favored. (c) 2006 Elsevier B.V. All rights reserved.
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Hartmann, S., M. Deppe, N. Oeschler, N. Caroca-Canales, J. G. Sereni, and C. Geibel. "Ferromagnetism in CePd1-xRhx single crystals." Journal of Optoelectronics and Advanced Materials 10, no. 7 (2008): 1607–1611.
Abstract: The orthorhombic CePd1-xRhx alloy exhibits a continuous evolution from a ferromagnetic ground state at x = 0 to
intermediate-valence behavior for x = 1. Here, we report on specific heat CP(T), resistivity Ï(T) and magnetization M(T)
measurements on single crystals in a Rh concentration range 0.2 < x < 0.65 exploring the ferromagnetic side of the
magnetic phase diagram. The transport and thermodynamic properties of the ferromagnetic phase have been investigated
in the temperature range from 300 K down to 0.35 K and analyzed in terms of a gap in the magnon spectrum and an
underlying Kondo contribution. Crystal electric field parameters are deduced from specific heat measurements well above
Tc- The competition between Kondo effect and ferromagnetism has been studied in dependence of the Rh concentration in
the system. Particularly, the enhanced Sommerfeld coefficient γ(x) indicates strong Kondo interactions when the Curie
temperature is reduced.
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Stockert, U., S. Hartmann, M. Deppe, N. Caroca-Canales, J. G. Sereni, C. Geibel, and F. Steglich. "Site dependence of the Kondo scale in CePd{1-x}Rhx due to Pd-Rh disorder." Physical Review B 92, no. 5 (2015): 054415.
Abstract: We present measurements of the thermopower S (T ) on CePd1 -xRhx between 2 K and 300 K. For low Rh content, the system behaves as a ferromagnetic Kondo system with a Curie temperature TC of about 6 K, a Kondo scale smaller than TC, and an overall crystal electric field splitting of 210 K. As the Rh content increases TC is suppressed, while the average Kondo scale gets larger. Simultaneously, the presence of different Ce environments leads to a broad distribution of local Kondo scales ranging from very small values to above 50 K. As a consequence, large thermopower values are observed over an extended temperature range. Close to the critical concentration we find power-law dependencies of S /T vs T down to 2 K. For a Rh content of x =0.95 we may show explicitly that the thermopower contains contributions from Ce sites with different local energy scales.
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