Person: Pérez García, Lucas
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First Name
Lucas
Last Name
Pérez García
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Física Aplicada
Identifiers
8 results
Search Results
Now showing 1 - 8 of 8
Item Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment(Applied physics letters, 2017) Ruiz Gómez, Sandra; Serrano, A.; Carabias,, I.; Garcıa, M. A.; Hernando Grande, Antonio; Mascaraque Susunaga, Arantzazu; Pérez García, Lucas; González Barrio, Miguel Ángel; Rodríguez de la Fuente, ÓscarWe have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single- crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity. Published by AIP Publishing.Item Helical surface magnetization in nanowires: the role of chirality(Nanoscale, 2020) Ruiz Gómez, Sandra; Fernández González, Claudia; Martínez, Eduardo; Raposo, Víctor; Sorrentino, Andrea; Foerster, Michael; Aballe, Lucía; Mascaraque Susunaga, Arantzazu; Ferrer, Salvador; Pérez García, LucasNanomagnetism is nowadays expanding into three dimensions, triggered by the discovery of new magnetic phenomena and their potential use in applications. This shift towards 3D structures should be accompanied by strategies and methodologies to map the tridimensional spin textures associated. We present here a combination of dichroic X-ray transmission microscopy at different angles and micromagnetic simulations allowing to determine the magnetic configuration of cylindrical nanowires. We have applied it to permalloy nanowires with equispaced chemical barriers that can act as pinning sites for domain walls. The magnetization at the core is longitudinal and generates at the surface of the wire helical magnetization. Different types of domain walls are found at the pinning sites, which respond differently to applied fields depending on the relative chirality of the adjacent domains.Item Geometrically defined spin structures in ultrathin Fe₃O₄ with bulk like magnetic properties(Nanoscale, 2018) Ruiz Gómez, Sandra; Pérez García, Lucas; Mascaraque Susunaga, Arantzazu; Quesada, Adrian; Prieto, Pilar; Palacio, Irene; Martín García, Laura; Foerster, Michael; Aballe, Lucía; Figuera, Juan de laWe have grown high quality magnetite microcrystals free from antiphase boundaries on Ru(0001) by reactive molecular beam epitaxy, conserving bulk magnetic properties below 20 nm thickness. Magnetization vector maps are obtained by X-ray spectromicroscopy and compared with micromagnetic simulations. The observed domain configurations are dictated purely by shape anisotropy, overcoming the possible influences of (magneto) crystalline anisotropy and defects, thus demonstrating the possibility of designing spin structures in ultrathin, magnetically soft magnetite at will.Item Tailoring the magnetization states in 2D arrays of multiresponse ferromagnetic nanomagnets(Journal of physics D: applied physics, 2017) Abuin Herráez, Manuel; Maicas, Marco; García, M Ángel; Pérez García, Lucas; Mascaraque Susunaga, ArantzazuWe have fabricated Fe52-54Co46-48 nanomagnet arrays as a function of several geometrical parameters like the spacing between nanostructures, the aspect ratio and the layers thicknesses. The nanomagnets consist in two magnetic layers, separated by a non magnetic interlayer, that interact through magnetostatic coupling. They present a multiresponse hysteresis loops with two different switching fields. We have performed micromagnetic simulations to discern the role play by the different interactions. The spacing in the array strongly modifies the saturating field along the short axis and the magnetization reversal mechanisms from coherent rotation to domain wall nucleation. A small asymmetry between the two magnetic layers favors a magnetization reversal mechanism along the long axis with two different switching fields. These fields can be tailored through the thickness of the layers or the inter-element spacing in the array. In trilayers with the same magnetic layer thicknesses, the asymmetry can be induced by growing the two magnetic layers with a different anisotropy. The well-defined reversal fields make these nanomagnets potentially useful for magnetic tagging.- Project number: 186
Item Desarrollo de herramientas para el aprendizaje interactivo y experimental del Electromagnetismo en el aula(2018) Pérez García, Lucas; Mascaraque Susunaga, Arantzazu; González Barrio, Miguel Angel; Varela del Arco, María; Rivera Calzada, Alberto Carlos; Ruiz Gómez, Sandra; Romero Izquierdo, Carlos; Rivera Folgado, Alba; Fernández Muñoz, Alejandro Item Asymmetrical magnetization processes induced by compositional gradients in ferromagnetic nanowires(Scripta Materialia, 2024) Fernández-González, Claudia; Berja, Alba; Álvaro-Gómez, Laura; Martín-Rubio, Carolina; Mascaraque Susunaga, Arantzazu; Aballe, Lucía; Sanz, Ruy; Ruiz-Gómez, Sandra; Pérez García, LucasElectrodeposited nanowires are an excellent scenario to study and control magnetic domain wall motion in nanostructures. In particular, the introduction of local changes in composition during the growth procedure has been proven to be very efficient for controlling the magnetization dynamics. In this work, we show the possibility of introducing compositional gradients in FeNi electrodeposited nanowires by gradually changing the Fe/Ni ratio along their axis. These compositional gradients produce an asymmetrical landscape for domain wall motion which is reflected in asymmetrical magnetization processes under an applied magnetic field. By studying nanowires with different compositional gradients we were able to correlate composition and magnetic asymmetry. Our results pave the way towards full control of the movement of domain walls along the nanowires.Item Highly Bi-doped Cu thin films with large spin-mixing conductance(APL Materials, 2018) Ruiz Gómez, Sandra; González Barrio, Miguel Ángel; Mascaraque Susunaga, Arantzazu; Pérez García, Lucas; Serrano, Aída; Guerrero, Rubén; Muñoz, Manuel; Lucas, Irene; Foerster, Michael; Aballe, LucíaThe spin Hall effect (SHE) provides an efficient tool for the production of pure spin currents, essentially for the next generation of spintronics devices. Giant SHE has been reported in Cu doped with 0.5% Bi grown by sputtering, and larger values are predicted for larger Bi doping. In this work, we demonstrate the possibility of doping Cu with up to 10% of Bi atoms without evidence of Bi surface segregation or cluster formation. In addition, YIG/BiCu structures have been grown, showing a spin mixing conductance larger that the one shown by similar Pt/YIG structures, reflecting the potentiality of these newmaterials.Item Observation of a topologically protected state in a magnetic domain wall stabilized by a ferromagnetic chemical barrier(Scientific reports, 2018) Ruiz Gómez, Sandra; Mascaraque Susunaga, Arantzazu; Pérez García, Lucas; Foerster, Michael; Aballe, Lucía; Proenca, M. P.; Lucas, Irene; Prieto, José Luis; Figuera, Juan de la; Quesada, AdriánThe precise control and stabilization of magnetic domain walls is key for the development of the next generation magnetic nano-devices. Among the multitude of magnetic configurations of a magnetic domain wall, topologically protected states are of particular interest due to their intrinsic stability. In this work, using XMCD-PEEM, we have observed a topologically protected magnetic domain wall in a ferromagnetic cylindrical nanowire. Its structure is stabilized by periodic sharp alterations of the chemical composition in the nanowire. The large stability of this topologically protected domain wall contrasts with the mobility of other non-protected and non-chiral states also present in the same nanowire. The micromagnetic simulations show the structure and the conditions required to find the topologically protected state. These results are relevant for the design of future spintronic devices such as domain wall based RF oscillators or magnetic memories.