Electronic and magnetic behaviors of Cr and Mn (co)-doped zinc-blende SiC compound

In this study, we have investigated the electronic and magnetic characteristics of doped and co-doped 3D SiC material using the main Korringa–Kohn–Rostoker (KKR) Green’s function technique combined with coherent potential approximation (CPA). Two impurities are considered, namely, chromium (Cr) and manganese (Mn), are considered. Density of state (DOS) calculations show that pure SiC is an N-type semiconductor with a 1.3eV band-gap energy, while substituting Si with Cr/Mn leads to a metallic behavior. Electronic structure calculations also reveal no magnetic order in the pure compounds, consistent with experiments. By comparing the energies of the ferromagnetic and spin-glass states, we have showed that impurities also induce ferromagnetism compounds. Furthermore, for each concentration, the polarization is determined from the density of carriers at the Fermi level. Finally, the Curie temperature ($$T_{C}$$) is calculated by the mean-field approach at concentrations near the percolation threshold. In both cases of Cr/Mn dopants, the value of $$T_{C}$$ is found to be greater than ambient temperature

The economic importance of Euterpe Oleracea Mart. (açaí), for the Arióca Pruanã/Oeiras do Pará extraction reserve

Brazil is among the countries responsible for supplying the açaí market in the world, and this fruit is used in the production of numerous products used for the most different purposes. Açaí, like other Amazonian products, has been gaining notoriety in the international economy not only for its Amazon benefits, but for the economic alternative of producing new market niches for large industries. Pará is the largest producer of açaí at the national level, with a turnover of more than R$460 million year. In the state, the largest production of the fruit is in the municipalities of Limoeiro do Ajuru (42 thousand tons) and Oeiras do Pará (26.5 thousand tons). In this sense, this research aimed to analyze the importance of açaí cultivation for farmers who live in the Arióca Pruanã extractive reserve, and what are the economic benefits that the sale of this fruit brings to the municipality's economy. The present research had as methodological framework the exploratory field investigation carried out in the extractive reserve Arióca Pruanã, at the points of collection of the fruit of the middlemen, as well as an interview with the community located in the reserve that maintains its way of life, from management to commercialization, becoming a fundamental part of the dynamic chain of production and distribution of açaí. The survey was conducted from June to August 2021. A questionnaire was developed and applied to 20 producers and 15 middlemen representing two different classes of individuals working in this trade: 20 to farmers and 15 to middlemen. The research identified that there are 2 main categories of agents that sell açaí within the reserve and that the açaí marketed comes from the floodplain areas surrounding the reserve. And that both the Oeiras and the Arióca rivers have potential for mass production of açaí. One of the main problems that weakens this production is the lack of technical assistance and projects aimed at family farming