222 research outputs found
Absence of ferromagnetic order in high quality bulk Co-doped ZnO samples
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Bulk Zn(1-x)Co(x)O samples were synthesized via standard solid-state reaction route with different Co molar concentrations up to 21%. A detailed microstructural analysis was carried out to investigate alternative sources of ferromagnetism, such as secondary phases and nanocrystals embedded in the bulk material. Conjugating different techniques we confirmed the Zn replacement by Co ions in the wurtzite ZnO structure, which retains, however, a high crystalline quality. No segregated secondary phases neither Co-rich nanocrystals were detected. Superconducting quantum interference device magnetometry demonstrates a paramagnetic Curie-Weiss behavior with antiferromagnetic interactions. We discuss the observed room temperature paramagnetism of our samples considering the current models for the magnetic properties of diluted magnetic semiconductors. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459885]1083FAPEMIGConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPEMIG_BrasilCNPq_BrasilFAPESP_Brasi
Adaptabilidade e estabilidade de híbridos de milho em 35 ambientes.
O objetivo deste trabalho foi avaliar a adaptabilidade e estabilidade de híbridos de milho em varias regiões do país
Status of global fits to neutrino oscillations
We review the present status of global analyses of neutrino oscillations,
taking into account the most recent neutrino data including the latest KamLAND
and K2K updates presented at Neutrino2004, as well as state-of-the-art solar
and atmospheric neutrino flux calculations. We give the two-neutrino solar +
KamLAND results, as well as two-neutrino atmospheric + K2K oscillation regions,
discussing in each case the robustness of the oscillation interpretation
against departures from the Standard Solar Model and the possible existence of
non-standard neutrino physics. Furthermore, we give the best fit values and
allowed ranges of the three-flavour oscillation parameters from the current
worlds' global neutrino data sample and discuss in detail the status of the
small parameters \alpha \equiv \Dms/\Dma as well as ,
which characterize the strength of CP violating effects in neutrino
oscillations. We also update the degree of rejection of four-neutrino
interpretations of the LSND anomaly in view of the most recent developments.Comment: v6: In the last Appendix we provide updated neutrino oscillation
results which take into account the relevant oscillation data released by the
MINOS and KamLAND collaboration
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