Spin-polarized electron tunneling in bcc FeCo/MgO/FeCo(001) magnetic tunnel junctions

In combining spin- and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe(1-x)Co(x)(001)/MgO/Fe(1-x)Co(x)(001) magnetic tunnel junctions. Contrary to previous theoretical predictions, we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic% as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Δ(1) symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe(1-x)Co(x)(001) free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system.     

EDXRF analysis of some samples of cigarette paper

The effects of tobacco on human health have been widely investigated and documented However, there are not too many specific reports on the potential risk associated to the presence of metals in the paper employed for cigarettes fabrication Even more, there is a lack of national and international norms in this respect. Otherwise, in the literature INAA appears as the unique method for wrapping paper analysis. Therefore, without a nuclear reactor available at the National University of Mexico (UNAM), EDXRF was selected with the aim to explore the possibility to apply this method, instead of INAA, to the analysis of wrapping paper assuming this task, at the beginning, as a supplement to a previous research which was recently presented (2005).¹ The analytical work was developed on the wrapping paper of eight of the most known marks of cigarettes in Mexico, in two non-destructive stages: a first survey, by the classical technique of energy dispersive X-ray fluorescence (EDXRF), used a 1 11 GB qradiation source of ²³⁸Pu and a SiLi detector. In the absence of standard reference materials for cigarette’s paper, the SRM-1832 and 1833 were required for calibration, a fiberglass air filter was used as a secondary standard. The second stage was performed in a spectrometer TX-2000, anode of Mo, quantification software EDXRF32 (fundamental parameters). This paper presents a comparison of the obtained values with those found in the literature. The results show that the EDXRF method, in the Mo tube version, has the adequate precision and detection limits for the analysis of wrapping paper.     

Effect of the medium in hexacyanoferrate (III)-iodide and peroxodisulfate-iodide reaction

The kinetics of the two reactions hexacyanoferrate (III)-iodide and peroxodisulfate-iodide in several isodielectric water-cosolvent mixtures have been studied. The results can be rationalized as a consequence of the cosolventwater interaction.

---

(III) -. -.

     

Determination of trace elements in blood samples by TXRF analysis

Trace elements were determined by TXRF in whole blood samples in a randomly non-occupational exposed population living in the Metropolitan Zone of the Mexico Valley (MZMV). Arithmetic and geometric means of S, Ca, Cu, Zn, Rb and Pb concentrations, were on the reported range values for non-occupational population in other countries, while those of K and Br were higher, possibly due to dietary habits and geographical or environmental factors. The noticeable decline in blood lead level (91%) should be positively perceived. As a part of the Quality Control Program, a certified IAEA-A13 was tested. This revised version was published online in August 2006 with corrections to the Cover Date.     

Photoemission of GaAs and InSb core levels

The energy distribution spectra of photoelectrons emitted from the 3d levels of Ga in GaAs and of4d of In in InSb by 40.8 and 48.4 eV photons is reported. These photons produce photoelectrons with very sharp thresholds, which can be used for an accurate determination of the binding energy of core levels with respect to the top of the valence bands.     

An unprecedented hybrid scorpionate/cyclopentadienyl ligand

An efficient method for the preparation of the first hybrid scorpionate/cyclopentadienyllithium compound as a new class of tridentate ligand is described. This compound is an excellent reagent for the introduction of this ligand into transition metal complexes.