23 research outputs found
Universal pinning energy barrier for driven domain walls in thin ferromagnetic films
We report a comparative study of magnetic field driven domain wall motion in
thin films made of different magnetic materials for a wide range of field and
temperature. The full thermally activated creep motion, observed below the
depinning threshold, is shown to be described by a unique universal energy
barrier function. Our findings should be relevant for other systems whose
dynamics can be modeled by elastic interfaces moving on disordered energy
landscapes.Comment: 10 pages, 3 figure
Resolving spin currents and spin densities generated by charge-spin interconversion in systems with reduced crystal symmetry
The ability to control the generation of spins in arbitrary directions is a long-sought goal in spintronics. Charge to spin interconversion (CSI) phenomena depend strongly on symmetry. Systems with reduced crystal symmetry allow anisotropic CSI with unconventional components, where charge and spin currents and the spin polarization are not mutually perpendicular to each other. Here, we demonstrate experimentally that the CSI in graphene-WTe induces spins with components in all three spatial directions. By performing multi-terminal nonlocal spin precession experiments, with specific magnetic fields orientations, we discuss how to disentangle the CSI from the spin Hall and inverse spin galvanic effects.We acknowledge support of the European Union's Horizon 2020 FET-PROACTIVE project TOCHA under Grant No. 824140 and of the Spanish Research Agency (AEI), Ministry of Science and Innovation, under Contracts No. PID2019-111773RB-I00/AEI/10.13039/501100011033, and SEV-2017-0706 Severo Ochoa. J F S acknowledges support from AEIunder contract RYC2019-028368-I/AEI/10.13039/50110001103, W S T and M V C from the European Union Horizon 2020 research and innovation program, Grant No. 881603 (Graphene Flagship), and I F A of a fellowship from 'la Caixa' Foundation (ID 100010434) with code LCF/BQ/DI18/11660030 and of H2020 Marie Skłodowska-Curie Grant No. 713673. J S acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 754558
Investigating the spin-orbit interaction in van der Waals heterostructures by means of the spin relaxation anisotropy
Graphene offers long spin propagation and, at the same time, a versatile platform to engineer its physical properties. Proximity-induced phenomena, taking advantage of materials with large spin-orbit coupling or that are magnetic, can be used to imprint graphene with large spin-orbit coupling and magnetic correlations. However, full understanding of the proximitized graphene and the consequences on the spin transport dynamics requires the development of unconventional experimental approaches. The investigation of the spin relaxation anisotropy, defined as the ratio of lifetimes for spins pointing out of and in the graphene plane, is an important step in this direction. This review discusses various methods for extracting the spin relaxation anisotropy in graphene-based devices. Within the experimental framework, current understanding on spin transport dynamics in single-layer and bilayer graphene is presented. Due to increasing interest, experimental results in graphene in proximity with high spin-orbit layered materials are also reviewed
Magnetism, spin dynamics, and quantum transport in two-dimensional systems
Two-dimensional (2D) quantum materials offer a unique platform to explore mesoscopic phenomena driven by interfacial and topological effects. Their tunable electric properties and bidimensional nature enable their integration into sophisticated heterostructures with engineered properties, resulting in the emergence of new exotic phenomena not accessible in other platforms. This has fostered many studies on 2D ferromagnetism, proximity-induced effects, and quantum transport, demonstrating their relevance for fundamental research and future device applications. Here, we review ongoing progress in this lively research field with special emphasis on spin-related phenomena
Geometrical control of pure spin current induced domain wall depinning
[EN] We investigate the pure spin-current assisted depinning of magnetic domain walls in half ring
based Py/Al lateral spin valve structures. Our optimized geometry incorporating a patterned
notch in the detector electrode, directly below the Al spin conduit, provides a tailored pinning
potential for a transverse domain wall and allows for a precise control over the magnetization
configuration and as a result the domain wall pinning. Due to the patterned notch, we are
able to study the depinning field as a function of the applied external field for certain applied
current densities and observe a clear asymmetry for the two opposite field directions.
Micromagnetic simulations show that this can be explained by the asymmetry of the pinning
potential. By direct comparison of the calculated efficiencies for different external field and
spin current directions, we are able to disentangle the different contributions from the spin
transfer torque, Joule heating and the Oersted field. The observed high efficiency of the pure
spin current induced spin transfer torque allows for a complete depinning of the domain wall
at zero external field for a charge current density of 6 1011 A m−2, which is attributed to the
optimal control of the position of the domain wall.Comisión Europea (P7-PEOPLE-2013-ITN 608031, FP7-ICT-2009-5)
Gobierno de España (MAT2014-52477-C5-4-P)
Junta de Castilla y Leon (SA090U16)
German Ministry for Education and Science (BMBF)
German Research Foundation (DFG) via the DFG collaborative research centre SFB/TRR 173 SPIN+X
Graduate School Material Science in Mainz (DFG/GSC 266)
European Research Council - MultiRev (665672)
Research Center of Innovative and Emerging Materials at Johannes Gutenberg University (CINEMA)
German Academic Exchange Service (DAAD) via the SpinNet Program 56268455
French RENATECH networ
Tunable room-temperature spin galvanic and spin Hall effects in van der Waals heterostructures
Spin-orbit coupling stands as a powerful tool to interconvert charge and spin
currents and to manipulate the magnetization of magnetic materials through the
spin torque phenomena. However, despite the diversity of existing bulk
materials and the recent advent of interfacial and low-dimensional effects,
control of the interconvertion at room-temperature remains elusive. Here, we
unequivocally demonstrate strongly enhanced room-temperature spin-to-charge
(StC) conversion in graphene driven by the proximity of a semiconducting
transition metal dichalcogenide(WS2). By performing spin precession experiments
in properly designed Hall bars, we separate the contributions of the spin Hall
and the spin galvanic effects. Remarkably, their corresponding conversion
effiencies can be tailored by electrostatic gating in magnitude and sign,
peaking nearby the charge neutrality point with a magnitude that is comparable
to the largest efficiencies reported to date. Such an unprecedented
electric-field tunability provides a new building block for spin generation
free from magnetic materials and for ultra-compact magnetic memory
technologies.Comment: 13 pages, 4 figure
Strongly anisotropic spin relaxation in graphene/transition metal dichalcogenide heterostructures at room temperature
Graphene has emerged as the foremost material for future two-dimensional
spintronics due to its tuneable electronic properties. In graphene, spin
information can be transported over long distances and, in principle, be
manipulated by using magnetic correlations or large spin-orbit coupling (SOC)
induced by proximity effects. In particular, a dramatic SOC enhancement has
been predicted when interfacing graphene with a semiconducting transition metal
dechalcogenide, such as tungsten disulphide (WS). Signatures of such an
enhancement have recently been reported but the nature of the spin relaxation
in these systems remains unknown. Here, we unambiguously demonstrate
anisotropic spin dynamics in bilayer heterostructures comprising graphene and
WS. By using out-of-plane spin precession, we show that the spin lifetime
is largest when the spins point out of the graphene plane. Moreover, we observe
that the spin lifetime varies over one order of magnitude depending on the spin
orientation, indicating that the strong spin-valley coupling in WS is
imprinted in the bilayer and felt by the propagating spins. These findings
provide a rich platform to explore coupled spin-valley phenomena and offer
novel spin manipulation strategies based on spin relaxation anisotropy in
two-dimensional materials
Interaction entre purs courant de spin et parois de domaine magnétiques dans des vannes latéral de spin
Ce manuscrit est basé sur l'étude de l'interaction entre des purs courants de spin et parois de domaines magnétiques. Cet étude a été divisée en quatre parties. Dans la première partie, nous avons donné une explication détaillée du transport de spin dans des nano structure métalliques en utilisant trois approches différentes. La deuxième partie est focalisée sur l'utilisation d'un pur courant de spin pour induire le mouvement d'un paroi de domaine. Dans la troisième et quatrième partie nous avons mis en évidence deux nouvelle techniques d'injection et détection de spin en utilisant des parois des domaines magnétiques.This thesis is based on the study of the interplay between pure spin currents and magnetic domains walls. This study has been divided in four chapters. In the first part, we provides a detailed explanation of the spin-transport in metallic structures by using three approaches. The second chapter concerns to the use of pure spin currents to induce DW motion in lateral spin valves. The third and four chapter, is mainly focused on the use of DWs for the efficient injection and detection of pure spin currents in lateral spin valves and cross shaped geometries
Calculation method of spin accumulations and spin signals in nanostructures using spin resistors
International audienceDetermination of spin accumulations and spin currents is essential for a deep understanding of spin transport in nanostructures and further optimization of spintronic devices. So far, they are easily obtained using different approaches in nanostructures composed of few elements; however their calculation becomes complicated as the number of elements increases. Here, we propose a 1-D spin resistor approach to calculate analytically spin accumulations, spin currents and magneto-resistances in heterostructures. Our method, particularly applied to multi-terminal metallic nanostructures, provides a fast and systematic mean to determine such spin properties in structures where conventional methods remain complex
Isotropic spin relaxation in graphene on hexagonal boron nitride
Resumen del póster presentado al 1st Workshop Spain-Taiwan: "2D Materials and Interfaces for Spintronics", celebrado en Barcelona (España) del 23 al 25 de octubre de 2017.We study the spin-lifetime anisotropy of spin-polarized carriers in graphene on top of hexagonal boron nitride (h-BN) using non-local lateral spin-valve devices (Figure 1) with a method that we recently developed. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we create an out of plane spin population by applying an oblique magnetic field and determine the relaxation of the non-precessing spin component (Figure 2). We find, within the experimental uncertainty, that the spin relaxation in graphene on boron nitride is isotropic, as it was previously found in graphene on SiO2. This result suggests that the substrate effects present on SiO2, which are expected to be absent or suppressed on h-BN, such as roughness, dangling bonds and charge traps, might play a minor role in making the spin relaxation isotropic and, more generally, in
the spin relaxation.Peer reviewe