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Personne

Arnaud Magrez

Education

PhD., Materials Science, summa cum laude, Université de Nantes, 2002

M.S., Chemistry, Université des Sciences et Technologies de Lille, 1999

Academic positions

Head of the Crystal Growth Facility, EPFL, 2012-present

Research Associate, Laboratoire de Physique de la Matière Complexe, EPFL, 2003-2012

Research Fellow, Peter Grunberg Institute, FZ-Juelich, 2002-2003

Administrative positions at EPFL

Scientific staff member, EPFL Assembly, 2015-present

Scientific staff member, School Council SB, 2014-present

Member of the IPHYS office 2016-present

Member of the ICMP office 2012-2015

Member of the safety committee of ICMP 2010-2015

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Domaines de recherche associés (97)

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Publications associées (190)

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PHYS-319: Physics lab IIIa

Ce cours permet d'observer de nombreux phénomènes physiques et leur applications technologiques. Il permet ainsi d'acquérir des connaissances sur les méthodes d'observation, de mesure et d'analyse des données. Les étudiants se familiarisent avec la communication scientifique.

PHYS-320: Physics lab IIIb

Imaging the Ultrafast Coherent Control of a Skyrmion Crystal

Priya Ranjan Baral, Fabrizio Carbone, Ping Che, Simone Gargiulo, Dirk Grundler, Ivan Madan, Arnaud Magrez, Henrik Moodysson Rønnow, Alexey Sapozhnik, Thomas Schönenberger

Exotic magnetic textures emerging from the subtle interplay between thermodynamic and topological fluctuation have attracted intense interest due to their potential applications in spintronic devices. Recent advances in electron microscopy enable the imaging of random photogenerated individual skyrmions. However, their deterministic and dynamical manipulation is hampered by the chaotic nature of such fluctuations and the intrinsically irreversible switching between different minima in the magnetic energy landscape. Here, we demonstrate a method to coherently control the rotation of a skyrmion crystal by discrete amounts at speeds which are much faster than previously observed. By employing circularly polarized femtosecond laser pulses with an energy below the band gap of the Mott insulator Cu2OSeO3, we excite a collective magnon mode via the inverse Faraday effect. This triggers coherent magnetic oscillations that directly control the rotation of a skyrmion crystal imaged by cryo-Lorentz transmission electron microscopy. The manipulation of topological order via ultrafast laser pulses shown here can be used to engineer fast spin-based logical devices.

2022

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Hidden bulk and surface effects in the spin polarization of the nodal-line semimetal ZrSiTe

Helmuth Berger, Alberto Crepaldi, Mauro Fanciulli, Gianmarco Gatti, Daniel Gosalbez Martinez, Marco Grioni, Arnaud Magrez, Oleg Yazyev

Local inversion symmetry breaking in centrosymmetric materials can lead to large spin polarization of the electronic band structure in separate sectors of the unit cell. Here, the authors reveal such hidden spin polarisation in ZrSiTe using spin and angle resolved photoemission spectroscopy in combination with ab initio band structure calculations and investigate the resultant spin polarised bulk and surface properties In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spin-orbit coupling (SOC) determines the spin polarization of the band structure. However, a local spin polarization can also arise in centrosymmetric crystals containing ISB subunits. This is namely the case for the nodal-line semimetal ZrSiTe where, by combining spin- and angle-resolved photoelectron spectroscopy with ab initio band structure calculations, we reveal a complex spin polarization. In the bulk, the valence and conduction bands exhibit opposite spin orientations in two spatially separated two-dimensional ZrTe sectors within the unit cell, yielding no net polarization. We also observe spin-polarized surface states that are well separated in energy and momentum from the bulk bands. A layer-by-layer analysis of the spin polarization allows us to unveil the complex evolution of the signal in the bulk states near the surface, thus bringing the intertwined nature of surface and bulk effects to the fore.

NATURE RESEARCH2021

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Viscoelastic behavior of suspensions of reduced graphene oxide nanoparticles in epoxy

László Forró, Yves Leterrier, Arnaud Magrez

The viscoelastic behavior of dilute suspensions of reduced graphene oxide (RGO) nanoparticles in a liquid SU8 epoxy dissolved in gamma butyrolactone was investigated at RGO concentrations in the range from 0.16 to 1.07 vol. %. Our results revealed that the addition of only 1 vol. % of RGO can increase the complex viscosity of the composites by up to 3 orders of magnitude, which is crucial for processing purposes. A marked shear thinning behavior with a yield stress was, moreover, found to emerge at low RGO concentrations for sonicated homogenized suspensions. This behavior was attributed to the partial polymerization of the epoxy and bonding between the epoxy rings and the residual functional groups on the RGO induced by the energy intensive ultrasound process that is key to achieve a good dispersion of the nanoparticles, in combination with the formation of a gel-like, percolated nanocomposite network. The percolation threshold and the aspect ratio of the RGO particles were derived from the analysis of the elastic shear modulus of the suspensions and found to be equal to 9 x 10(-4) and 500, respectively. We attribute this extremely with low percolation threshold to the restriction of the polymer chain mobility within the well dispersed, high aspect ratio RGO network.

AMER INST PHYSICS2021

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Nanotube de carbone

thumb|Représentation d'un nanotube de carbone. (cliquer pour voir l'animation tridimensionnelle). thumb|Un nanotube de carbone monofeuillet. thumb|Extrémité d'un nanotube, vue au microscope électroniq

Transition de phase

vignette|droite|Noms exclusifs des transitions de phase en thermodynamique. En physique, une transition de phase est la transformation physique d'un système d'une phase vers une autre, induite par la

Graphène

Le graphène est un matériau bidimensionnel cristallin, forme allotropique du carbone dont l'empilement constitue le graphite. Cette définition théorique est donnée par le physicien en 1947. Par la