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

Scale-invariant large nonlocality in polycrystalline graphene

The observation of large nonlocal resistances near the Dirac point in graphene has been related to a variety of intrinsic Hall effects, where the spin or valley degrees of freedom are controlled by symmetry breaking mechanisms. Engineering strong spin or valley Hall signals on scalable graphene devices could stimulate further practical developments of spin- and valleytronics. Here we report on scale-invariant nonlocal transport in large-scale chemical vapour deposition graphene under an applied external magnetic field. Contrary to previously reported Zeeman spin Hall effect, our results are explained by field-induced spin-filtered edge states whose sensitivity to grain boundaries manifests in the nonlocal resistance. This phenomenon, related to the emergence of the quantum Hall regime, persists up to the millimeter scale, showing that polycrystalline morphology can be imprinted in nonlocal transport. This suggests that topological Hall effects in large-scale graphene materials are highly sensitive to the underlying structural morphology, limiting practical realizations.Comment: Main paper (14 pages, 5 figures) and Supplementary information (8 pages, 8 figures

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

Tuning the resistive switching properties of TiO2-x films

We study the electrical characteristics of TiO2-x-based resistive switching devices fabricated with different oxygen/argon flow ratio during the oxide thin film sputtering deposition. Upon minute changes in this fabrication parameter, three qualitatively different device characteristics were accessed in the same system, namely, standard bipolar resistive switching, electroforming-free devices, and devices with multi-step breakdown. We propose that small variations in the oxygen/ argon flow ratio result in relevant changes of the oxygen vacancy concentration, which is the key parameter determining the resistive switching behavior. The coexistence of percolative or non-percolative conductive filaments is also discussed. Finally, the hypothesis is verified by means of the temperature dependence of the devices in low resistance state.Fil: Ghenzi, Néstor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. CIC nanoGUNE; EspañaFil: Rozenberg, M.J.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Université Paris Sud; FranciaFil: Llopis, R.. CIC nanoGUNE; EspañaFil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hueso, Luis E.. Universidad del País Vasco; España. Fundación Vasca para la Ciencia; EspañaFil: Stoliar, Pablo Alberto. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. CIC nanoGUNE; Españ