Measurement of thin film magnetostriction using field-dependent atomic force microscopy

Measurement of thin film magnetostriction is a challenging task, as magnetostrictive material deformations in parts per million, in conjunction with materials at small dimensions, require high precision, often with dedicated set-ups, for reproducible results. We have developed a novel approach employing a commercial atomic force microscope (AFM) with attached electromagnets. Magnetostriction measurements are demonstrated on 50 - 500 nm thick Fe81Al19 films sputter deposited directly on high aspect ratio commercial AFM micro-cantilevers. A magnetostrictive deflection of the cantilever bimorph translates into a deflection force acting in a contact mode measurement, which is interpreted and recorded as a change in height. For determination of the magnetostriction coefficient, we have developed a modified version of the equation for the magnetostrictive deflection of a cantilever bimorph by Guerrero and Wetherhold, taking into account long-range attractive forces acting during contact mode AFM measurements in air. The sub-atomic precision of the AFM, combined with the widespread availability of all components and the simple set-up, makes the measurement of magnetostriction on films of just a few tens of nanometers thickness easily accessible.H2020-MSCA-ITN-2014 SELECTA (grant agreement no. 642642 of the European Commission

Unraveling the properties of sharply defined submicron scale FeCu and FePd magnetic structures fabricated by electrodeposition onto electron-beam-lithographed substrates

In this work, Fe–X (X = Cu, Pd) submicron-scale structures were electrodeposited onto pre-patterned substrates prepared by e-beam lithography. The FeCu and FePd (with reduced Pd content) systems were investigated as attractive candidates for a variety of potential applications in magnetic data storage and biomedicine. Confined growth in the restricted cavities resulted in a nanoscale grain size leading to well-defined geometries with sharp edges and corners and an average height of up to 215 nm. Specifically, nine 100 μm × 100 μm arrays of three geometries (cylindrical, rectangular and cruciform) in three different sizes were created. In addition, the total deposition time ranged from 3.5 s (FeCu) to 200 s (FePd), i.e. much faster than by traditional physical vapor deposition approaches and was performed at ambient conditions. Magnetic force microscopy for the cylindrical and cruciform structures revealed virtually no contrast at zero field, suggesting magnetic curling effects (instead of coherent rotation) during magnetization reversal. These curling effects result in low values of remanent magnetization, which is advantageous in minimizing dipolar interactions between the structures either when they are deposited onto the substrate or eventually dispersed in a liquid (e.g. in biomedical applications, as drug delivery carriers, where particle agglomeration is undesirable)

Electrochemical Synthesis, Magnetic and Optical Characterisation of FePd Dense and Mesoporous Nanowires

Dense and mesoporous FePd nanowires (NWs) with 45 to 60 at.% Pd content were successfully fabricated by template- and micelle-assisted pulsed potentiostatic electrodeposition using nanoporous anodic alumina and polycarbonate templates of varying pore sizes. An FePd electrolyte was utilized for obtaining dense NWs while a block copolymer, P-123, was added to this electrolyte as the micelle-forming surfactant to produce mesoporous NWs. The structural and magnetic properties of the NWs were investigated by electron microscopy, X-ray diffraction, and vibrating sample magnetometry. The as-prepared NWs were single phase with a face-centered cubic structure exhibiting 3.1 µm to 7.1 µm of length. Mesoporous NWs revealed a core-shell structure where the porosity was only witnessed in the internal volume of the NW while the outer surface remained non-porous. Magnetic measurements revealed that the samples displayed a soft ferromagnetic behavior that depended on the shape anisotropy and the interwire dipolar interactions. The mesoporous core and dense shell structure of the NWs were seen to be slightly affecting the magnetic properties. Moreover, mesoporous NWs performed excellently as SERS substrates for the detection of 4,4'-bipyridine, showing a low detection limit of 10 −12 M. The signal enhancement can be attributed to the mesoporous morphology as well as the close proximity of the embedded NWs being conducive to localized surface plasmon resonance

A comparative study of the influence of the deposition technique (electrodeposition versus sputtering) on the properties of nanostructured Fe70Pd30 films

Sputtering and electrodeposition are among the most widespread techniques for metallic thin film deposition. Since these techniques operate under different principles, the resulting films typically show different microstructures even when the chemical composition is kept fixed. In this work, films of Fe70Pd30 were produced in a thickness range between 30 and 600 nm, using both electrodeposition and sputtering. The electrodeposited films were deposited under potentiostatic regime from an ammonia sulfosalicylic acid-based aqueous solution. Meanwhile, the sputtered films were deposited from a composite target in radio frequency regime. Both approaches were proven to yield high quality and homogenous films. However, their crystallographic structure was different. Although all films were polycrystalline and Fe and Pd formed a solid solution with a body-centered cubic structure, a palladium hydride phase was additionally detected in the electrodeposited films. The occurrence of this phase induced internal stress in the films, thereby influencing their magnetic properties. In particular, the thickest electrodeposited Fe70Pd30 films showed out-of-plane magnetic anisotropy, whereas the magnetization easy axis lied in the film plane for all the sputtered films. The domain pattern of the electrodeposited films was investigated by magnetic force microscopy. Finally, nanoindentation studies highlighted the high quality of both the sputtered and electrodeposited films, the former exhibiting higher reduced Young’s modulus and Berkovich hardness values

Frequency-dependent stimulated and post-stimulated voltage control of magnetism in transition metal nitrides: towards brain-inspired magneto-ionics

Magneto-ionics, which deals with the change of magnetic properties through voltage-driven ion migration, is expected to be one of the emerging technologies to develop energy-efficient spintronics. While a precise modulation of magnetism is achieved when voltage is applied, much more uncontrolled is the spontaneous evolution of magneto-ionic systems upon removing the electric stimuli (i.e., post-stimulated behavior). Here, we demonstrate a voltage-controllable N ion accumulation effect at the outer surface of CoN films adjacent to a liquid electrolyte, which allows for the control of magneto-ionic properties both during and after voltage pulse actuation (i.e., stimulated and post-stimulated behavior, respectively). This effect, which takes place when the CoN film thickness is below 50 nm and the voltage pulse frequency is at least 100 Hz, is based on the trade-off between generation (voltage ON) and partial depletion (voltage OFF) of ferromagnetism in CoN by magneto-ionics. This novel effect may open opportunities for new neuromorphic computing functions, such as post-stimulated neural learning under deep sleep.Financial support by the European Research Council (MAGIC-SWITCH 2019-Proof of Concept Grant, Agreement No. 875018), the European Union's Horizon 2020 research and innovation programme (European Training Network, BeMAGIC ETN/ITN Marie Skłodowska-Curie grant No. 861145; and Integrated Infrastructure, RADIATE, grant No. 824096), the Spanish Government (MAT2017-86357-C3-1-R, PID2020-116844RB-C21 and PDC2021-121276-C3), the Generalitat de Catalunya (2017-SGR-292 and 2018-LLAV-00032), the European Regional Development Fund (MAT2017-86357-C3-1-R and 2018-LLAV-00032) and the KU Leuven (BOF program) is acknowledged. A. Q. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities through the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S) and the Juan de la Cierva formación contract (FJC2019-039780-I). J. S. thanks the Spanish Fábrica Nacional de Moneda y Timbre (FNMT) for fruitful discussions. The XAS measurements were performed at BL29-BOREAS beamline at ALBA Synchrotron with the collaboration of ALBA staff. We acknowledge service from MiNa Laboratory at IMN, and funding from CM (project S2018/NMT-4291 TEC2SPACE), MINECO (project CSIC13-4E-1794) and EU (FEDER, FSE). E. M. is a Serra Húnter Fellow.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Encoding magnetic states in monopole-like configurations using superconducting dots

A large manifold of nontrivial spin textures, including the stabilization of monopole-like fields, are generated by using a completely new and versatile approach based on the combination of superconductivity and magnetism. Robust, stable, and easily controllable complex spin structures are encoded, modified, and annihilated in a continuous magnetic thin film by defining a variety of magnetic states in superconducting dots

En France et en Italie, archives de terrain et terrain d’archives

Enregistrement, conservation, numérisation, restitution : de sa captation au retour potentiel aux communautés qui les ont produites, les archives sonores d’intérêt ethnomusicologique posent des questions déontologiques et éthiques majeures quant à leur gestion et valorisation. Issus de programmes de recherches scientifiques ou de collectes associatives ou militantes, conservés dans des institutions locales ou nationales, ces documents sont sujets à des politiques institutionnelles différenciées. Ainsi, la comparaison d’archives concernant de mêmes régions (et avec parfois les mêmes témoins), conservées dans des centres d’archives différents, peut être délicate. Dans cet article il s’agira de réfléchir sur les possibilités de comparaison de corpus similaires. Notre propos sera illustré par une recherche multisite entre la Maison méditerranéenne des sciences de l’homme à Aix-en-Provence (France) et l’Istituto Centrale per i Beni Sonori e Audiovisivi de Rome (Italie).From their capture to their return (ideally) to the communities that produced them, sound archives of ethnomusicological interest raise major deontological and ethical issues regarding their management and valorisation. This paper will consider the possibilities of comparing similar corpora archived in different archive centres. It will be illustrated by a multisite research between the Maison Méditerranéenne des Sciences de l’homme in Aix-en-Provence (France) and the Istituto Centrale per i Beni Sonori e Audiovisivi in Rome (Italy)

Expériences et actualités en direct du Cines : retour sur la journée utilisateurs du 21 septembre 2018

La sixième édition de la journée utilisateurs PAC (Plateforme d’Archivage au CINES) s’est tenue au Cines  à Montpellier le 21 septembre. Deux grands axes y étaient développés : les questions et actualités relatives à l’archivage sur le long terme et  le retour d'expérience des utilisateurs. Avant de revenir sur ce qui s'est dit durant cette journée, il nous semble important de souligner qu'un débat reste ouvert, à savoir que recouvre exactement le terme d’archivage numérique pérenne ? Peut-..

Dive into Europeana to listen to the sea

In December, the Centre national de la recherche scientifique (CNRS) present music and sound archive collections, picked up from the following centres : Centre de recherche en ethnomusicologie (CREM), the Centre de Recherche sur l’Espace Sonore et l’environnement urbain (CRESSON) and from the phonothèque de la Maison Méditerranéenne des Sciences de l’Homme (MMSH). The CNRS preserves and disseminates field investigations materials produced by researchers in humanities and social sciences. We m..