The phase diagram of 2D antiferromagnets

The magnetic phase diagram of thin-layered antiferromagnets is revealed experimentally by investigating the tunnelling conductance as a function of magnetic field. A rich magnetic behaviour in CrCl3 is uncovered, from which relevant magnetic information is extracted that is not easily available with other approaches

Observen un fenomen magnètic amb possibles aplicacions en computació

En un article publicat en l'última edició de Nature Materials, científics de l'Institut Català de Nanotecnologia (ICN) dirigits per l'investigador ICREA i professor de la UAB Sergio O. Valenzuela, confirmen l'observació d'un elusiu fenomen físic, l'anomenat arrossegament de magnons. Es tracta d'un efecte termoelèctric que els científics fa 50 anys que intenten aïllar. El seu control obre les portes a millores en generadors compactes d'energia elèctrica i en el desenvolupament de memòries magnètiques

Magnon-drag thermopile

arXiv:1203.5628v1Thermoelectric effects in spintronics are gathering increasing attention as a means of managing heat in nanoscale structures and of controlling spin information by using heat flow. Thermal magnons (spin-wave quanta) are expected to play a major role; however, little is known about the underlying physical mechanisms involved. The reason is the lack of information about magnon interactions and of reliable methods to obtain it, in particular for electrical conductors because of the intricate influence of electrons. Here, we demonstrate a conceptually new device that enables us to gather information on magnon–electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon-drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. This information is crucial to understand the physics of electron–magnon interactions, magnon dynamics and thermal spin transport.This research was supported by the Spanish Ministerio de Ciencia e Innovación, MICINN (MAT2010-18065) and by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement NANOFUNCTION no 257375.Peer Reviewe

Enhanced spin signal in nonlocal devices based on a ferromagnetic CoFeAl alloy

The Creative Commons Attribution 3.0 Unported License to their work.We systematically study the nonlocal spin signal in lateral spin valves based on CoFeAl injectors and detectors and compare the results with identically fabricated devices based on CoFe. The devices are fabricated by electron beam evaporation at room temperature. We observe a > 10-fold enhancement of the spin signal in the CoFeAl devices. We explain this increase as due to the formation of a highly spin-polarized Co2FeAl Heusler compound with large resistivity. These results suggest that Heusler compounds are promising candidates as spin polarized electrodes in lateral spin devices for future spintronic applications.We acknowledge the financial support from the Spanish Ministerio de Ciencia e Innovación, MICINN (MAT2010-18065, FIS2009-06671-E, and GICSERV program “Access to ICTS integrated nano- and microelectronics cleanroom”). J.V.d.V. acknowledges the support from FWO-VL.Peer Reviewe

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

Molecular Approach for Engineering Interfacial Interactions in Magnetic/Topological Insulator Heterostructures

Altres ajuts: Interreg V-A España-Francia-Andorra (EFA 194/16 TNSI)Controlling interfacial interactions in magnetic/topological insulator heterostructures is a major challenge for the emergence of novel spin-dependent electronic phenomena. As for any rational design of heterostructures that rely on proximity effects, one should ideally retain the overall properties of each component while tuning interactions at the interface. However, in most inorganic interfaces, interactions are too strong, consequently perturbing, and even quenching, both the magnetic moment and the topological surface states at each side of the interface. Here, we show that these properties can be preserved using ligand chemistry to tune the interaction of magnetic ions with the surface states. By depositing Co-based porphyrin and phthalocyanine monolayers on the surface of BiTe thin films, robust interfaces are formed that preserve undoped topological surface states as well as the pristine magnetic moment of the divalent Co ions. The selected ligands allow us to tune the interfacial hybridization within this weak interaction regime. These results, which are in stark contrast with the observed suppression of the surface state at the first quintuple layer of BiSe induced by the interaction with Co phthalocyanines, demonstrate the capability of planar metal-organic molecules to span interactions from the strong to the weak limit

Pulse calibration and non-adiabatic control of solid-state artificial atoms

Transitions in an artificial atom, driven non-adiabatically through an energy-level avoided crossing, can be controlled by carefully engineering the driving protocol. We have driven a superconducting persistent-current qubit with a large-amplitude, radio-frequency field. By applying a bi-harmonic waveform generated by a digital source, we demonstrate a mapping between the amplitude and phase of the harmonics produced at the source and those received by the device. This allows us to image the actual waveform at the device. This information is used to engineer a desired time dependence, as confirmed by detailed comparison with simulation.Comment: 4.1 pages, 3 figure