Room temperature ferromagnetic-like behavior in Mn-implanted and post-annealed InAs layers deposited by Molecular Beam Epitaxy

We report on the magnetic and structural properties of Ar and Mn implanted InAs epitaxial films grown on GaAs (100) by Molecular Beam Epitaxy (MBE) and the effect of Rapid Thermal Annealing (RTA) for 30 seconds at 750C. Channeling Particle Induced X- ray Emission (PIXE) experiments reveal that after Mn implantation almost all Mn atoms are subsbtitutional in the In-site of the InAs lattice, like in a diluted magnetic semiconductor (DMS). All of these samples show diamagnetic behavior. But, after RTA treatment the Mn-InAs films exhibit room-temperature magnetism. According to PIXE measurements the Mn atoms are no longer substitutional. When the same set of experiments were performed with As as implantation ion all of the layers present diamagnetism without exception. This indicates that the appearance of room-temperature ferromagnetic-like behavior in the Mn-InAs-RTA layer is not related to lattice disorder produce during implantation, but to a Mn reaction produced after a short thermal treatment. X-ray diffraction patterns (XRD) and Rutherford Back Scattering (RBS) measurements evidence the segregation of an oxygen deficient-MnO2 phase (nominally MnO1.94) in the Mn-InAs-RTA epitaxial layers which might be on the origin of room temperature ferromagnetic-like response observed.Comment: 16 pages, 5 figures. Acepted in J. Appl. Phy

Geometría, estructuras y evolución de la terminación occidental de los relieves del Orógeno Alpino-Pirenaico (NO Península Ibérica)

The geometry, structures and tectonic evolution of the western termination of the Alpine-Pyrenean Orogen relief onshore and related foreland have been studied. We present the results of structural mapping and detailed outcrop studies of Cenozoic-age structures carried out at the NW Iberian Peninsula. On the basis of this work we propose a new tectonic model for the termination. According to the identified structures, three main regions could be recognised: (1) the Astur-Galaica (AG) region or the western part of the Cantabrian Mountains (CM), characterised by thrusts with a south vergence, which are the continuation of the structures of the Pyrenees, (2) The Galaico-Leoneses Mountains (GLM), characterized by thrusts with a north vergence, and (3) The Rías Baixas-Terra Chá region (RBT) characterized by strike-slip faults with no relevant associated relief but with recent seismic activity, which represents the less deformed Alpine foreland. The western termination of the Alpine-Pyrenean Orogen is formed due to the superposition of two mountain ranges (CM and GLM) and a complex tectonic evolution. The CM were emplaced southwards and subsequently the GLM was emplaced northwards. The western limit of the E-W thrusts of the CM and the associated relief define a N-S-oriented arch-shape structures (Ibias-Ancares and Rúa-Vilalba). Tectonic activity commenced during the Eocene, and in the westernmost areas during the Late Oligocene. The CM south-verging thrust activity ended at the beginning of Late Miocene, although deformation continued in the GLM with north-verging thrusts. The evidence of intense tectonic activity during the Miocene, the western migration and southward transference of tectonic activity and the interaction of two successive deformation fronts, suggests that a re-examination of the tectonic evolution of the northern Iberian microplate during the Alpine Orogeny is necessary.Se han estudiado las estructuras, la geometría y la evolución tectónica de la terminación occidental de los relieves del Orógeno Alpino-Pirenaico (o Cántabro Pirenaicos) y del antepaís asociado. Se presentan los resultados de la cartografía estructural y estudios detallados de campo de las estructuras tectónicas cenozoicas del NO de la Península Ibérica. Basándose en este estudio proponemos un nuevo modelo tectónico para esta terminación. En función de las estructuras tectónicas identificadas se han diferenciado tres regiones: (1) la Astur-Galaica que es la terminación más occidental de la Cordillera Cantábrica (CC) y que se caracteriza por cabalgamientos con vergencia sur y por ser la continuación natural de las estructuras que configuran el Pirineo. (2) Los Montes Galaico-Leoneses (MGL) que se caracteriza por cabalgamientos con vergencia norte. Finalmente, (3) la región de las Rías Bajas-Terra Cha que se caracteriza por fallas de desgarre con sismicidad asociada que no generan relieve importante y que representan el antepaís menos deformado. La terminación del Orógeno Alpino-Pirenaico es el resultado de la superposición de dos cadenas montañosas: la Cordillera Cantábrica (CC) que es prolongación de los Pirineos y los Montes Galaico Leoneses (MGL), con una compleja evolución tectónica. La CC se emplazó hacia el sur y posteriormente fueron los MGL los que se emplazaron hacia el norte. El límite occidental de los cabalgamientos de dirección E-O que elevan la CC son dos estructuras arqueadas de dirección N-S (Ibias-Ancares y Rúa-Vilalba). La actividad tectónica comenzó durante el Eoceno y en las zonas más occidentales es durante el Oligoceno. La actividad de los cabalgamientos de la CC finalizó al principio del Mioceno superior. Mientras tanto, la deformación continuó en los cabalgamientos de los MGL que se emplazaban hacia el norte. Las evidencias de intensa actividad tectónica durante el Mioceno, la migración hacia el oeste y la transferencia de la deformación hacia el sur, así como la interacción de dos frentes de deformación sucesivos, sugiere una revisión de la evolución tectónica del norte de la microplaca Ibérica durante la Orogenia Alpina

A dark energy multiverse

We present cosmic solutions corresponding to universes filled with dark and phantom energy, all having a negative cosmological constant. All such solutions contain infinite singularities, successively and equally distributed along time, which can be either big bang/crunchs or big rips singularities. Classicaly these solutions can be regarded as associated with multiverse scenarios, being those corresponding to phantom energy that may describe the current accelerating universe

Lorentzian wormholes generalize thermodynamics still further

This paper deals with some thermodynamical aspects of Lorentzian wormholes, including the formulation of the three main laws and the consideration of a possible thermal emission made up of some sort of phantom radiation coming out from the wormhole at a negative temperature. In order for these topics to be consistently developed we have used a 2+2 formalism first advanced by Hayward for spherically symmetric spacetimes, where a generalized surface gravity is defined on the trapping horizon. Our results generalize still further those of the already generalized gravitational thermodynamics. © 2009 IOP Publishing Ltd.This work was supported by a Spanish MEC Research Project No. FIS2008-06332/FIS.Peer Reviewe