1,251 research outputs found
Gradual transition from insulator to semimetal of CaEuB with increasing Eu concentration
The local environment of Eu (, ) in
CaEuB () is investigated by
means of electron spin resonance (ESR). For the spectra show
resolved \textit{fine} and \textit{hyperfine} structures due to the cubic
crystal \textit{electric} field and nuclear \textit{hyperfine} field,
respectively. The resonances have Lorentzian line shape, indicating an
\textit{insulating} environment for the Eu ions. For , as increases, the ESR lines broaden due to local
distortions caused by the Eu/Ca ions substitution. For , the lines broaden further and the spectra gradually change from
Lorentzian to Dysonian resonances, suggesting a coexistence of both
\textit{insulating} and \textit{metallic} environments for the Eu ions.
In contrast to CaGdB, the \textit{fine} structure is still
observable up to . For the \textit{fine} and
\textit{hyperfine} structures are no longer observed, the line width increases,
and the line shape is purely Dysonian anticipating the \textit{semimetallic}
character of EuB. This broadening is attributed to a spin-flip scattering
relaxation process due to the exchange interaction between conduction and
Eu electrons. High field ESR measurements for
reveal smaller and anisotropic line widths, which are attributed to magnetic
polarons and Fermi surface effects, respectively.Comment: Submitted to PR
B- and C-type low molecular weight glutenin subunits in tetraploid wheat germplasm
General knowledge acquisition entails the extraction of statistical regularities from the environment. At high levels of complexity, this may involve the extraction, and consolidation, of associative regularities across event memories. The underlying neural mechanisms would likely involve a hippocampo-neocortical dialog, as proposed previously for system-level consolidation. To test these hypotheses, we assessed possible differences in consolidation between associative memories containing cross-episodic regularities and unique associative memories. Subjects learned face-location associations, half of which responded to complex regularities regarding the combination of facial features and locations, whereas the other half did not. Importantly, regularities could only be extracted over hippocampus-encoded, associative aspects of the items. Memory was assessed both immediately after encoding and 48 h later, under fMRI acquisition. Our results suggest that processes related to system-level reorganization occur preferentially for regular associations across episodes. Moreover, the build-up of general knowledge regarding regular associations appears to involve the coordinated activity of the hippocampus and mediofrontal regions. The putative cross-talk between these two regions might support a mechanism for regularity extraction. These findings suggest that the consolidation of cross-episodic regularities may be a key mechanism underlying general knowledge acquisition
Fermion soliton stars
A real scalar field coupled to a fermion via a Yukawa term can evade no-go
theorems preventing solitonic solutions. For the first time, we study this
model within General Relativity without approximations, finding static and
spherically symmetric solutions that describe fermion soliton stars. The Yukawa
coupling provides an effective mass for the fermion, which is key to the
existence of self-gravitating relativistic solutions. We systematically study
this novel family of solutions and present their mass-radius diagram and
maximum compactness, which is close to (but smaller than) that of the
corresponding Schwarzschild photon sphere. Finally, we discuss the ranges of
the parameters of the fundamental theory in which the latter might have
interesting astrophysical implications, including compact (sub)solar and
supermassive fermion soliton stars for a standard gas of degenerate neutrons
and electrons, respectively.Comment: 16 pages, 5 figure
Diffusive-like effects and possible non trivial local topology on the half-Heusler YPdBi compound
FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFINEP - FINANCIADORA DE ESTUDOS E PROJETOSThe non-ambiguous experimental identification of topological states of matter is one of the main interesting problems regarding this new quantum state of matter. In particular, the half-Heusler family RMT (R = rare-earth, T = Pd, Pt or Au and T = Bi, Sb, Pb or Sn) could be a useful platform to explore these states due to their cubic symmetry and the topological properties tunable via their unit cell volume and/or the nuclear charges of the M and T atoms. In this work, we report electron spin resonance (ESR) and complementary macroscopic measurements in the Nd3+-doped putative topologically trivial semimetal YPdBi. Following the Nd3+ ESR lineshape as a function of microwave power, size of the particle and temperature, we have been able to observe an evolution from a Dysonian lineshape to a diffusive-like lineshape. Furthermore, the Nd3+ ESR intensity saturation is concentration dependent, which could be due to a phonon-bottleneck process. Comparing these results with the Nd3+-doped YPtBi, we discuss a possible scenario in which the Nd3+ ions could locally tune the topological properties of the system.8516FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFINEP - FINANCIADORA DE ESTUDOS E PROJETOS2013/17427-72012/04870-72006/60440-02009/09247-32010/11949-32011/01564-02011/23650-52012/05903-6442230/2014-1304649/2013-9sem informaçãosem informação62. Annual Conference on Magnetism and Magnetic Materials (MMM)2017Pittsburgh, PAIEEE Magnetics SocietyAIP Publishin
- …