4,987 research outputs found
Magnetic-field effects in defect-controlled ferromagnetic Ga_{1-x}Mn_xAs semiconductors
We have studied the magnetic-field and concentration dependences of the
magnetizations of the hole and Mn subsystems in diluted ferromagnetic
semiconductor Ga_{1-x}Mn_xAs. A mean-field approximation to the hole-mediated
interaction is used, in which the hole concentration p(x) is parametrized in
terms of a fitting (of the hole effective mass and hole/local moment coupling)
to experimental data on the Tc critical temperature. The dependence of the
magnetizations with x, for a given temperature, presents a sharply peaked
structure, with maxima increasing with applied magnetic field, which indicates
that application to diluted-magnetic-semiconductor devices would require
quality-control of the Mn-doping composition. We also compare various
experimental data for Tc(x) and p(x) on different Ga_{1-x}Mn_xAs samples and
stress the need of further detailed experimental work to assure that the
experimental measurements are reproducible.Comment: RevTeX 4, 3 two-column pages, 4 colour figures; to appear in J Appl
Phy
Robot at factory lite - a step-by-step educational approach to the robot assembly
In a robotics scope, an excellent way to test and improve knowledge is through competitions. In other words, it is possible to follow the results in practice, compare them with the development of other teams and improve the current solutions. The Robot At Factory Lite proposal simulates an Industry 4.0 warehouse scenario, applying education through Science, Technology, Engineering, and Mathematics (STEM) methodology, where the participants have to work on a solution to overcome its challenges. Thus, this article presents an initial electromechanical proposal, which is the basis for developing robots for this competition. The presented main concepts aim to inform the possibilities of using the robot’s parts and components. Thus, an idea can be sketched in the participants’ minds, inspiring them to use their imagination and knowledge through the presentation of this model.The authors are grateful to the Foundation for Science and Technology (FCT,
Portugal) for financial support through national funds FCT/MCTES (PIDDAC)
to CeDRI (UIDB/05757/2020 and UIDP/05757/2020), SusTEC (LA/P/0007/
2021). The project that gave rise to these results received the support of a
fellowship from ”la Caixa” Foundation (ID 100010434). The fellowship code is
LCF/BQ/DI20/11780028.info:eu-repo/semantics/publishedVersio
Hole concentration in a diluted ferromagnetic semiconductor
We consider a mean-field approach to the hole-mediated ferromagnetism in
III-V Mn-based semiconductor compounds to discuss the dependence of the hole
density on that of Mn sites in Ga_{1-x}Mn_xAs. The hole concentration, p, as a
function of the fraction of Mn sites, x, is parametrized in terms of the
product m*J_{pd}^2 (where m* is the hole effective mass and J_{pd} is the
Kondo-like hole/local-moment coupling), and the critical temperature Tc. By
using experimental data for these quantities, we have established the
dependence of the hole concentration with x, which can be associated with the
occurrence of a reentrant metal-insulator transition taking place in the hole
gas. We also calculate the dependence of the Mn magnetization with x, for
different temperatures (T), and found that as T increases, the width of the
composition-dependent magnetization decreases drammatically, and that the
magnetization maxima also decreases, indicating the need for quality-control of
Mn-doping composition in diluted magnetic semiconductor devices.Comment: 4 pages, 3 figures, RevTeX 3; Fig. 1 changed, new references adde
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