Search results for " Circular"

Dibujando una nueva cartografía de la colonialidad Sur-Norte en época de crisis: la reproducción de la episteme y el estilo de vida europeo en las mi…

2018

El artículo analiza la migración de cualificados españoles a los espacios de Educación Superior ecuatoriana desde 2010 a 2016, con el objetivo de entender la experiencia de movilidad cualificada española hacia Ecuador. Para ello se ha utilizado una metodología cualitativa a través de entrevistas semiestructuradas a españoles y ecuatorianos que trabajan en los espacios de la Educación Superior. Además, se ha complementado con encuestas online autoadministradas y con observación participante. Se concluye que entre España y Ecuador se han creado espacios de circularidad promovidos por un contexto de crisis económica en España y por una gran inversión en la Educación Superior ecuatoriana. Sin e…

Dismantling and electrochemical copper recovery from Waste Printed Circuit Boards in H2SO4–CuSO4–NaCl solutions

2019

Abstract The worldwide growing of electrical and electronic equipment makes increasingly urgent to find environmentally friendly treatments for e-waste. In this paper, the attention has been focused on i) the eco-friendly dismantling of the electronic components from Waste Printed Circuit Boards and ii) recovering of pure metallic copper, which is the most abundant metal and one of the most valuable in Printed Circuit Boards. After an experimental optimization study, we found that a solution containing 0.5 M H2SO4, 0.4 M CuSO4, and 4 M NaCl can be successfully used to disassemble the electronic components from the boards by leaching of all exposed metals. Air was blown into the leaching sol…

Structure and polarized absorption spectra of Mn3+-substituted andalusites (viridines)

1977

Al driven peculiarities of local coordination and magnetic properties in single phase Alx CrFeCoNi high entropy alloys

2021

The authors thank the Helmholtz-Zentrum Berlin for the provision of access to synchrotron radiation facilities and allocation of synchrotron radiation at the PM2-VEKMAG, BAMline, and UE46_PGM-1 beamlines of BESSY II at HZB as well as measurement time for magnetometry at HZB CoreLab for Quantum Materials. A. S. acknowledges personal funding from CALIPSOplus project (the Grant Agreement no. 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020). The financial support for the VEKMAG project and the PM2-VEKMAG beamline by the German Federal Ministry for Education and Research (Nos. BMBF 05K10PC2, 05K10WR1, 05K10KE1) and by HZB is cordially acknowledged by all co-author…

Correlation of local disorder and electronic properties in the Heusler alloy Co2Cr0.6Fe0.4Al

2007

For the fully ordered Heusler alloy Co2Cr0.6Fe0.4Al half-metallic ferromagnetism has been predicted. Local disorder other than the Al–Cr/Fe (B2)-type disorder is known to destroy the half-metallic bandgap. The usage of appropriate buffer layers improves the structural quality of thin films. We correlate the structural properties of thin magnetron sputtered films determined by x-ray diffraction with details of the x-ray magnetic circular dichroism spectra. From the value of the magnetic moment located at the Cr atom and features of the Co absorption spectra we conclude that the buffer layers lead also to an improvement in the local atomic order. The atomic ordering gradually approaches the l…

Temperature dependence of x-ray absorption spectra in the ferromagnetic Heusler alloysMn2VAlandCo2FeAl

2010

We investigate the temperature dependence of the spin-resolved unoccupied density of states (DOS) in ferromagnetic ${\text{Co}}_{2}\text{FeAl}$ and ferrimagnetic ${\text{Mn}}_{2}\text{VAl}$ epitaxial films on MgO(100) using x-ray magnetic circular dichroism. We observe an unexpected strong temperature dependence of the DOS beyond the change expected from the Fermi distribution function. An increase in spectral weight is observed for majority states below the Fermi energy in the case of ${\text{Mn}}_{2}\text{VAl}$ and for minority states above the Fermi energy in the case of ${\text{Co}}_{2}\text{FeAl}$. Reduced atomic order near the interface suppresses the unexpected temperature dependence…

Effect of annealing on Co2FeAl0.5Si0.5thin films: A magneto-optical and x-ray absorption study

2011

A series of Al and MgO-capped Co${}_{2}$FeAl${}_{0.5}$Si${}_{0.5}$ epitaxial thin films grown on MgO with various levels of L2${}_{1}$ ordering was obtained by in situ annealing. The films were studied by means of x-ray absorption spectroscopy, x-ray magnetic circular dichroism (XMCD), magneto-optical Kerr effect magnetometry, and Brillouin light scattering. We find the anisotropy constants decrease, while the spin wave stiffness increases as the samples are annealed to higher temperatures. The magnetization as determined by Brillouin light scattering reveals a maximum value at intermediate annealing temperatures. Surprisingly, the orbital-to-spin-moment ratio (as seen from XMCD) is essenti…

Threshold photoemission magnetic circular dichroism at the spin-reorientation transition of ultrathin epitaxial Pt/Co/Pt(111)/W(110) films

2009

X-ray magnetic circular dichroism (MCD) is nowadays widely used for the investigation of magnetic properties of surfaces and thin films. Recently, similarly large effects have been observed for UV-VIS MCD effects both in single [1] and two-photon photoemission [2-3]. This threshold MCD effect is directly related to spin-orbit effects present at the Fermi edge. We report on the observation of threshold photoemission magnetic circular dichroism (TPMCD) in one-photon and two-photon photoemission (1PPE and 2PPE) at a Pt-capped ultrathin Co wedge grown on Pt(111)/W(110) using femtosecond laser light. TPMCD measurements result in asymmetries continuously increasing with the sample thickness. This…

Photocatalytic activity of non-stoichiometric ZnFe2O4under visible light irradiation

2014

Nanostructured zinc ferrites with different excess iron contents (ZnFe2+zO4, where z = 0.00, 0.05, 0.10 and 0.15) have been synthesized using the sol–gel auto-combustion method. The effect of excess iron on the structural, optical and visible light photocatalytic activity of zinc ferrite samples has been investigated. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), x-ray magnetic circular dichroism (XMCD), Brunauer–Emmett–Teller theory, scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV–Vis) and photoluminescence spectroscopy were used to characterize the synthesized non-stoichiometric ZnFe2O4 powders. The XRD patterns demonstrated that the samples con…

Element-Selective Magnetic Imaging in Exchange-Coupled Systems by Magnetic Photoemission Microscopy

1998

We have used a photoemission microscope to obtain element-resolved magnetic contrast in stacked magnetic thin film systems. Magnetic information is thereby provided by X-ray magnetic circular dichroism. Elemental sensitivity, which is crucial for studying magnetic coupling phenomena in systems with several different layers, is achieved by tuning the energy of the illuminating photons to atomic absorption edges. We present measurements of a Ni-coated Co micropattern on Cu(001), and a wedged Co/Cr/Fe(001) sample. In the former sample the Ni magnetization is seen to follow the magnetization of the Co pattern, thereby changing from an out-of-plane easy axis in areas without underlying Co to in…