ULTIMATE-I

The second is the meeting between ULTIMATE-I and NESTOR, both Research and Innovation Staff Exchange (RISE) projects from Marie Skłodowska-Curie Action involving researchers from Spain and Argentina, amount other countries, from left to right: Alejandro Butera, Myriam Aguirre (both ULTIMATE-I) and Gerardo Goya and Enio Lima Jr (NESTOR), both RISE project at Instituto de Nanociencia y Materiales de Aragón (INMA).

ULTIMATE-I secondment to Senzor Infiz of Sindy J. Rodríguez Sotelo (Instituto de Física del Litoral IFIS-CONICET, Santa Fe, Argentina).

The secondment was used to explore interactions directing the self-assembly of magnetic nanocubes and prepare the publication with Carlos Garcia (CCTVal, Universidad Técnica Federico Santa María, Valparaíso, Chile). Also, a prolonged stay in Senzor Infiz was used to discuss the modelling of production processes, particularly the exfoliation of two-dimensional materials.

The results of the secondment are presented at the German Physical Society annual conference from 26 March to 31 March 2023 on the campus of the Technical University Dresden. The conference was organized by the Condensed Matter Section of the society.

• Sindy Rodríguez (CONICET); oral presentation: “Formation model of AlF3 intercalated aggregates on HOPG surfaces for rechargeable battery applications”; authors: S.J. Rodríguez, I. Stanković, A.E. Candia, M.C.G. Passeggi and G.Ruano

• Sindy Rodríguez (CONICET); poster presentation: “Assembly of iron oxide nanocuboids directed by surface, ligand and magnetic interactions”

ULTIMATE-I researchers from Argentina, Luis Avilés and Julián Milano from CNEA / @Resonanlab / Instituto Balseiro, Bariloche win Argentinian national PICT projects in #spintronics and magnetic materials.

Two projects are funded by the Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación.

The topics of the projects are Spin Dynamics in Micro- and Nanostructures (Luis Avilé) and Control of acoustic and spin wave propagation through ferromagnetic thin films with periodic domain patterns (Julian Milano).

The goal of the projects is to investigate the spin transport phenomena in magnetic micro- and nanostructures for the generation, detection and control of spin currents!

Looking forward to the results of these projects!

Manipulating the magnetization of materials on extremely short time scales, in the picosecond range, is a highly coveted grail for information technologies. The complex magneto-optical techniques currently used are difficult to integrate spintronics into devices. To overcome these constraints, Juan Carlos Rojas-Sánchez of the Institut Jean Lamour (CNRS/Université de Lorraine) and one of the PIs of the ULTIMATE-I project has received an ERC Consolidator grant for his Magnetallien project.

In spintronics, components are controlled by a quantum parameter of electrons: the spin. This approach promises much more powerful and energy-efficient integrated circuits and components but faces many technical challenges.

“To achieve this goal, I am interested in materials where there is a strong coupling between spin and orbit,” explains Juan Carlos Rojas-Sánchez, a CNRS researcher at the Institut Jean Lamour (CNRS/Université de Lorraine). For example, when an electric current is passed through a platinum nanowire, it scatters the electrons in opposite directions according to their spin orientation, creating a spin current that can be injected into an adjacent magnetic layer. This phenomenon has applications such as memories, sensors or the realization of logic circuits.

Different approaches are envisaged to study and control this key ingredient: the spin-orbit coupling. For example, by generating a spin current in a thin layer of magnetic material and injecting it into a neighbouring layer. Understanding and exploiting this phenomenon on the picosecond time scale remains a challenge. It is currently only possible to obtain a signal of up to a hundred gigahertz using lasers and particularly “heavy” optical means,” notes Juan Carlos Rojas-Sanchez. I want to reduce the cost and size of the devices by exploiting new physical systems that use spin-orbit interaction.

To this end, he has set up the MAGNETALLIEN project, for which he has just been awarded this ERC Consolidator grant.

Original in French: https://factuel.univ-lorraine.fr/node/22436

Friday, December 16, at 11 a.m. Buenos Aires Time, Prof. Dr José Santiso gave a seminar entitled “Strain effects in vanadium dioxide films with the metal-insulator electronic transition” at “Laboratorio de Física de Superficies e Interfaces”, Instituto de Física del Litoral (IFIS-Litoral, CONICET-UNL).

José Santiso is a researcher at the Catalan Institute of Nanoscience and Nanotechnology (ICN2) in Barcelona, Spain. Dr Santiso, invited by Dr Mario C. G. Passeggih is part of the ULTIMATE-I (Ultra Thin Magneto Thermal Sensoring) project supported by the European Union.

The following is a brief summary.

Vanadium dioxide (VO₂)is an archetypical material showing a metal-insulator (M-I) Mott transition at about T=68C with several orders of magnitude change in the resistivity between the semiconducting low-T M1 phase and the high-T metallic rutile R phase. It has been proposed as a good candidate directly for Resistive-Random Access Memory (RRAM) devices or as complementary selector in combination of a bipolar RRAM device because of its high on/off ratio, fast switching speed and high current density. Although in bulk form the transition is above room temperature either chemical doping or mechanical strain have been demonstrated to bring the transition closer or even below room temperature making it very attractive in different devices. This work studies the structure features across transition of high quality strained epitaxial VO₂ films deposited on isostructural rutile TiO₂ (001) single crystals. Since M-I transition in VO₂ is accompanied by a structural change between monoclinic M1 phase and tetragonal R phase, with substantial variation in cell parameters, the nucleation of the high-T R phase embedded in the low-T M1 phase during transition, is expected to generate local interfacial regions with a large strain. The characterization of the structural features of the films by means of synchrotron X-ray Diffraction upon thermal cycles revealed the formation of local strain effects during the phase transition in competition with the epitaxial strain induced by the growth on the mismatched TiO₂ substrates. Such interphase regions between M1 and R crystal domains are submitted to a uniaxial strain (overlapped to the biaxial in-plane epitaxial strain) that stabilizes other polytypic VO₂ insulating phases (monoclinic M2, and triclinic transitional M3 or T phase) beyond their expected stability regions.[1] Concomitant to the subtle structural distortions a slight rotation of the monoclinic crystal domains occurs to accommodate the elastic energy constraints. The persistence of the coexistence of those polytypic phases even at room temperature turns VO₂ into a complex heterogeneous material. Nonetheless, at conditions where XRD of the films seems to indicate a pure rutile R phase, HRTEM analysis revealed a certain degree of heterogeneity at the nanoscale forming an intricate tweed pattern of other polytypes with different arrangements of V-V dimers along the c-axis direction [2], still displaying a metallic character. Altogether these observations evidence that VO₂ micro and nanostructure, and therefore its electrical response, depends on a subtle balance of unconventional strain relaxation mechanisms.

[1] L. Rodríguez, F. Sandiumenge, C. Frontera, J.M. Caicedo, J. Padilla, G. Catalán, J. Santiso, Strong strain gradients and phase coexistence at the metal-insulator transition in VO₂ epitaxial films, Acta Mater. 220 (2021) 117336.

[2] F. Sandiumenge, L. Rodríguez, M. Pruneda, C. Magén, J. Santiso, G. Catalan, Metallic Diluted Dimerization in VO₂ Tweeds, Adv. Mater. 33 (2021) 2004374.