Modelling spin waves in noncollinear antiferromagnets: spin-flop states, spin spirals, skyrmions and antiskyrmions

Spin waves in antiferromagnetic materials have great potential for next-generation magnonic technologies. However, their properties and their dependence on the type of ground-state antiferromagnetic structure are still open questions. Here, we investigate theoretically spin waves in one- and two-dimensional model systems with a focus on noncollinear antiferromagnetic textures such as spin spirals and skyrmions of opposite topological charges. We address in particular the nonreciprocal spin excitations recently measured in bulk antiferromagnet $\alpha$--$\text{Cu}_2\text{V}_2\text{O}_7$ utilizing inelastic neutron scattering experiments [Phys.\ Rev.\ Lett.\ \textbf{119}, 047201 (2017)], where we help to characterize the nature of the detected spin-wave modes. Furthermore, we discuss how the Dzyaloshinskii-Moriya interaction can lift the degeneracy of the spin-wave modes in antiferromagnets, resembling the electronic Rashba splitting. We consider the spin-wave excitations in antiferromagnetic spin-spiral and skyrmion systems and discuss the features of their inelastic scattering spectra. We demonstrate that antiskyrmions can be obtained with an isotropic Dzyaloshinskii-Moriya interaction in certain antiferromagnets.Comment: 26 pages, 9 figure

First-principles investigation of spin wave dispersions in surface-reconstructed Co thin films on W(110)

We computed spin wave dispersions of surface-reconstructed Co films on the W(110) surface in the adiabatic approximation. The magnetic exchange interactions are obtained via first-principles electronic structure calculations using the Korringa-Kohn-Rostoker Green function method. We analyze the strength and oscillatory behavior of the intralayer and interlayer magnetic interactions and investigate the resulting spin wave dispersions as a function of the thickness of Co films. In particular, we highlight and explain the strong impact of hybridization of the electronic states at the Co-W interface on the magnetic exchange interactions and on the spin wave dispersions. We compare our results to recent measurements based on electron energy loss spectroscopy [E. Michel, H. Ibach, and C.M. Schneider, Phys. Rev. B 92, 024407 (2015)]. Good overall agreement with experimental findings can be obtained by considering the possible overestimation of the spin splitting, stemming from the local spin density approximation, and adopting an appropriate correction.Comment: 14 pages, 14 figure

A biodiversity information system in an open data/metadatabase architecture

This thesis presents an overview of biological collections, their complexity and related bio-information management activities in the main institutes in the Amazon region

The success factors for SMEs: Empirical evidence

This paper empirically analyzes the success factors for SMEs. Particularly, the paper intends to analyze if firm age, human resource costs, debt, venture capital funding, investment in innovation and productivity are success factors for SMEs. The effects were tested using static and dynamic panel data, on a data set of 200 Portuguese SMEs. The use of dynamic panel data is important in order to control for: endogeneity; time-invariant characteristics; possible collinearity between independent variables; effects from possible omission of independent variables; elimination of non-observable individual effects; and, the correct estimation of the relationship between the dependent variable in the previous and current periods. Our results reveal a positive impact on success of: human resource costs; investments in innovation; productivity; and, venture capital funding. We also confirm the negative impact of firm age and debt. Also, the results show evidence of persistence in success for the case of one of the success proxies used

Métodos de prestação de cuidados

A prestação de cuidados insere-se no seio de uma constelação de fenómenos e acontecimentos. As características da maioria das instituições de saúde, as estruturas de organização, as múltiplas fontes de poder, os valores quantitativos centrados na produtividade tornaram-se, com a marcha do tempo, inadaptados ao crescimento e ao desenvolvimento da organização dos cuidados de saúde. Numerosos sinais se fizeram sentir. Os recursos financeiros insuficientes, o pessoal desmotivado e insatisfeito, as taxas de absentismo e de mobilidade crescentes e o esgotamento do pessoal que cuida caracterizaram os nossos serviços de saúde custosos, mas desumanizados, centrados na técnica e na doença. Esqueceu-se a pessoa, o cliente, a família e o enfermeiro que cuida. Então, quais são os ambientes que podem promover o respeito e a dignidade das pessoas, assim como o compromisso e a presença dos enfermeiros ao lado das pessoas que vivem experiências de saúde? Quais são os cuidados que favorecem os processos interactivos e terapêuticos dirigidos a manter, recuperar e promover a saúde? Quais são os métodos de prestação de cuidados que, ao mesmo tempo, podem assegurar a melhoria da qualidade do cuidado e a vitalidade da organização