Tuning the crystalline electric field and magnetic anisotropy along the CeCuBi2−x_{2-x}Sbx_{x} series

We have performed X-ray powder diffraction, magnetization, electrical resistivity, heat capacity and inelastic neutron scattering (INS) to investigate the physical properties of the intermetallic series of compounds CeCuBi$_{2-x}$Sb$_{x}$. These compounds crystallize in a tetragonal structure with space group $P4/nmm$ and present antiferromagnetic transition temperatures ranging from 3.6 K to 16 K. Remarkably, the magnetization easy axis changes along the series, which is closely related to the variations of the tetragonal crystalline electric field (CEF) parameters. This evolution was analyzed using a mean field model, which included anisotropic nearest-neighbor interactions and the tetragonal CEF Hamiltonian. The CEF parameters were obtained by fitting the magnetic susceptibility data with the constraints given by the INS measurements. Finally, we discuss how this CEF evolution can affect the Kondo physics and the search for a superconducting state in this family.Comment: 7 pages, 6 figures. To be published in Physical Review

Electronic and magnetic properties of stoichiometric CeAuBi2

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESWe report the electronic and magnetic properties of stoichiometric CeAuBi2 single crystals. At ambient pressure, CeAuBi2 orders antiferromagnetically below a Neel temperature (T-N) of 19 K. Neutron diffraction experiments revealed an antiferromagnetic pro1012117FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES2015/15665-32017/10581-12017/25269-32018/11364-72019/04196-3304496/2017-0Sem informaçãoThis work was supported by the São Paulo Research Foundation (FAPESP) Grants No. 2015/15665-3, No. 2017/10581-1, No. 2017/25269-3, No. 2018/11364-7, No. 2019/04196-3, CNPq Grant No. 304496/2017-0, and CAPES, Brazil. The experimental and theoretical work

Spatial point analysis based on dengue surveys at household level in central Brazil

<p>Abstract</p> <p>Background</p> <p>Dengue virus (DENV) affects nonimunne human populations in tropical and subtropical regions. In the Americas, dengue has drastically increased in the last two decades and Brazil is considered one of the most affected countries. The high frequency of asymptomatic infection makes difficult to estimate prevalence of infection using registered cases and to locate high risk intra-urban area at population level. The goal of this spatial point analysis was to identify potential high-risk intra-urban areas of dengue, using data collected at household level from surveys.</p> <p>Methods</p> <p>Two household surveys took place in the city of Goiania (~1.1 million population), Central Brazil in the year 2001 and 2002. First survey screened 1,586 asymptomatic individuals older than 5 years of age. Second survey 2,906 asymptomatic volunteers, same age-groups, were selected by multistage sampling (census tracts; blocks; households) using available digital maps. Sera from participants were tested by dengue virus-specific IgM/IgG by EIA. A Generalized Additive Model (GAM) was used to detect the spatial varying risk over the region. Initially without any fixed covariates, to depict the overall risk map, followed by a model including the main covariates and the year, where the resulting maps show the risk associated with living place, controlled for the individual risk factors. This method has the advantage to generate smoothed risk factors maps, adjusted by socio-demographic covariates.</p> <p>Results</p> <p>The prevalence of antibody against dengue infection was 37.3% (95%CI [35.5–39.1]) in the year 2002; 7.8% increase in one-year interval. The spatial variation in risk of dengue infection significantly changed when comparing 2001 with 2002, (ORadjusted = 1.35; p < 0.001), while controlling for potential confounders using GAM model. Also increasing age and low education levels were associated with dengue infection.</p> <p>Conclusion</p> <p>This study showed spatial heterogeneity in the risk areas of dengue when using a spatial multivariate approach in a short time interval. Data from household surveys pointed out that low prevalence areas in 2001 surveys shifted to high-risk area in consecutive year. This mapping of dengue risks should give insights for control interventions in urban areas.</p