Temperature dependence of spin polarization in ferromagnetic metals using lateral spin valves

A high reproducibility in the performance of cobalt/copper and permalloy/copper lateral spin valves with transparent contacts is obtained by optimizing the interface quality and the purity of copper. This allows us to study comprehensively the spin injection properties of both ferromagnetic materials, as well as the spin transport properties of copper, which are not affected by the used ferromagnetic material, leading to long spin diffusion lengths. Spin polarizations of permalloy and cobalt are obtained as a function of temperature. Analysis of the temperature dependence of both the spin polarization and conductivity of permalloy using the standard two-channel model for ferromagnetic metals suggests that a correction factor of ~2 is needed for the spin polarization values obtained by lateral spin valve experiments.Comment: 16 pages, 5 figures, 1 tabl

Contribution of defects to the spin relaxation in copper nanowires

The contributions to the spin relaxation in copper (Cu) nanowires are quantified by carefully analyzing measurements of both charge and spin transport in lateral spin valves as a function of temperature and thickness. The temperature dependence of the spin-flip scattering solely arises from the scattering with phonons, as in bulk Cu, whereas we identify grain boundaries as the main temperature-independent contribution of the defects in the nanowires. A puzzling maximum in the spin diffusion length of Cu at low temperatures is found, which can be explained by the presence of magnetic impurities. The results presented here suggest routes for improving spin transport in metallic nanostructures, otherwise limited by confinement effects.Comment: 10 pages, 4 figures, 1 tabl

Trampas de Pobreza en Argentina: Evidencia Empírica a Partir de un Pseudo Panel

The aim of this paper is to analyze the existence of poverty traps in Argentina. In order to do it so, the income dynamic was estimated by using a pseudo panel built from the Encuesta Permanente de Hogares. This methodology allows to overcome econometric challenges involved in testing for the presence of poverty traps: lack of long duration panels, attrition, and measurement error in income. The results do find no evidence for the existence of poverty traps due to nonlinearities in income dynamics. El objetivo del presente trabajo es analizar la existencia de trampas de pobreza en Argentina. Para ello se estima la dinámica de ingresos a partir de un pseudo panel construido con información brindada por la Encuesta Permanente de Hogares. Esta metodología permite superar los problemas econométricos que enfrenta la estimación de trampas de pobreza: carencia de un panel para un periodo largo de tiempo, attrition y la presencia de errores no clásicos de medición en los ingresos. Los resultados encontrados descartan la existencia de trampas de pobreza debido a no linealidades en la dinámica de ingresos.Trampas de pobreza, dinámica de ingresos, pseudo panel, Argentina.

The airbnb effect on the rental market: The case of Madrid

Trabajo Fin de Grado. Curso Académico 2018-2019. Grado en Economía. Calificado con Matrícula de Honor.The debate over Airbnb is increasingly gaining attention both in academic and non-academic spheres. However, in specialized literature almost all analyses have ignored the spatial dependence behind it, that is, when landlord’s decisions to raise or keep prices are related to each other. In the City of Madrid, non-spatial and spatial regressions were compared over individual rental prices. Results suggest that traditional models were biased and, once contemplating these effects, the impact of Airbnb is no longer significant. The causes could be the lower profitability, lack of legal guarantees and a strong competition of professional hosts. As a result, there are less incentives to displace dwellings from the rental market and push rental prices u

Temperature dependence of spin diffusion length and spin Hall angle in Au and Pt

We have studied the spin transport and the spin Hall effect as a function of temperature for platinum (Pt) and gold (Au) in lateral spin valve structures. First, by using the spin absorption technique, we extract the spin diffusion length of Pt and Au. Secondly, using the same devices, we have measured the spin Hall conductivity and analyzed its evolution with temperature to identify the dominant scattering mechanisms behind the spin Hall effect. This analysis confirms that the intrinsic mechanism dominates in Pt whereas extrinsic effects are more relevant in Au. Moreover, we identify and quantify the phonon-induced skew scattering. We show that this contribution to skew scattering becomes relevant in metals such as Au, with a low residual resistivity.Comment: 13 pages, 5 figure

Tailoring palladium nanocontacts by electromigration

Electromigration is employed in nanoelectronics for transforming narrow metallic wires into electrodes separated by a few nanometers gap. In this work, we fabricate either nanoconstrictions or nanogap electrodes by performing electromigration in palladium nanowires. The device resistance and the cross section of the initial nanowires allow us to regulate the conditions for transforming deterministically each nanowire in a specific final device. The resulting samples show unique electrical transport characteristics and could be used in multiple nanoelectronics research applications, from ballistic transport to electrodes for single molecular devices.Fil: Arzubiaga, Libe. CIC nanoGUNE; EspañaFil: Golmar, Federico. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llopis, Roger. CIC nanoGUNE; EspañaFil: Casanova, Félix. CIC nanoGUNE; España. Basque Foundation for Science; EspañaFil: Hueso, Luis E.. CIC nanoGUNE; España. Basque Foundation for Science; Españ

Interfacial mechanism in the anomalous Hall effect of Co/Bi2_2O3_3 bilayers

Oxide interfaces are a source of spin-orbit coupling which can lead to novel spin-to-charge conversion effects. In this work the contribution of the Bi$_2$O$_3$ interface to the anomalous Hall effect of Co is experimentally studied in Co/Bi$_2$O$_3$ bilayers. We evidence a variation of 40% in the AHE of Co when a Bi$_2$O$_3$ capping layer is added to the ferromagnet. This strong variation is attributed to an additional source of asymmetric transport in Co/Bi$_2$O$_3$ bilayers that originates from the Co/Bi$_2$O$_3$ interface and contributes to the skew scattering.Comment: 7 pages, 4 figure