46 research outputs found
Symmetry breaking effects in spin(orbit)tronic systems: from universality of anisotropic magnetoresistance in in-plane anisotropy systems to chiral Dzyaloshinskii-Moriya interaction effects in epitaxial metallic and graphene-based perpendicular anisotropy systems
Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 22-09-2017Esta tesis tiene embargado el acceso al texto completo hasta el 22-03-201
Tuning domain wall velocity with Dzyaloshinskii-Moriya interaction
We have studied a series of Pt/Co/M epitaxial trilayers, in which Co is
sandwiched between Pt and a non magnetic layer M (Pt, Ir, Cu, Al). Using polar
magneto-optical Kerr microscopy, we show that the field- induced domain wall
speeds are strongly dependent on the nature of the top layer, they increase
going from M=Pt to lighter top metallic overlayers, and can reach several 100
m/s for Pt/Co/Al. The DW dynamics is consistent with the presence of chiral
N\'eel walls stabilized by interfacial Dzyaloshinskii-Moriya interaction (DMI)
whose strength increases going from Pt to Al top layers. This is explained by
the presence of DMI with opposite sign at the Pt/Co and Co/M interfaces, the
latter increasing in strength going towards heavier atoms, possibly due to the
increasing spin-orbit interaction. This work shows that in non-centrosymmetric
trilayers the domain wall dynamics can be finely tuned by engineering the DMI
strength, in view of efficient devices for logic and spitronics applications.Comment: 5 pages, 4 Figure
Mejora de hábitos saludables en universitarios del Grado de Enfermería a través del aprendizaje colaborativo y las TIC
El grupo de investigación “Salud Pública-Estilos de Vida, Metodología Enfermera y Cuidados en el Entorno Comunitario” de la Universidad Complutense, Facultad de Enfermería, Fisioterapia y Podología, siguiendo con su línea de investigación sobre hábitos saludables en la población española, ha diseñado un proyecto de innovación docente con objetivos similares y que abarque otra vertiente diferente pero a la vez complementaria. A través de un aprendizaje colaborativo, en el que se fomenten habilidades sociales y académicas, se intenta conseguir una interacción de calidad entre los estudiantes y el profesorado para generar conocimiento colectivo útil a la comunidad estudiantil. El aprendizaje colaborativo pone en práctica una serie de competencias que permiten obtener un gran beneficio al desarrollar competencias emocionales y sociales así como la autonomía, la responsabilidad y el propio autocontrol en el aprendizaje.
Consiste en una forma de organización de pequeños grupos de trabajo dado por alumnos que desean desempeñar una labor en conjunto. La responsabilidad en el aprendizaje es cosa del grupo que desempeña el trabajo propuesto y no tanto en el profesorado. Asimismo el uso y desarrollo de herramientas que permiten el “m-learning” en cualquier momento y desde cualquier espacio geográfico permite estar en contacto continuo alumnos y profesorado. Herramientas orientadas a la creación de videos de corta duración o infografías serán fundamentales en el aprendizaje colaborativo, en la adquisición de conocimientos y habilidades relacionadas con los hábitos saludables y las nuevas tecnologías. Durante los meses de enero a mayo de 2020, los estudiantes del curso seleccionado elaboraron infografías a través de las cuales fomentarán los hábitos saludables descritos en este documento. Hicieron uso de mailings masivos al resto de alumnos/as del Grado correspondiente. Tras finalizar se administró un cuestionario para valorar la efectividad de la actividad y la calidad de la misma
Note: Vectorial-magneto optical Kerr effect technique combined with variable temperature and full angular range all in a single setup
Here, we report on a versatile full angular resolved/broad temperature range/vectorial magneto optical Kerr effect (MOKE) magnetometer, named TRISTAN. Its versatility relies on its capacity to probe temperature and angular dependencies of magnetization reversal processes without the need to do any intervention on the apparatus during measurements. The setup is a combination of a vectorial MOKE bench and a cryostat with optical access. The cryostat has a motorized rotatable sample holder with azimuthal correction. It allows for simultaneous and quantitative acquisition of the two in-plane magnetization components during the hysteresis loop at different temperatures from 4 K up to 500 K and in the whole angular range, without neither changing magnet orientation nor opening the cryostat. Measurements performed in a model system with competing collinear biaxial and uniaxial contributions are presented to illustrate its capabilitiesP.P. acknowledges financial support from MINECO through Contract No. JCI-2011- 09602. F.J.T. acknowledges financial support from Ramon y Cajal program (RYC-2011-09617). This work has been supported by MINECO through Project Nos. MAT2011-25598 and MAT2012-39308, by the Comunidad de Madrid through Project No. S2013/MIT-2850 NANOFRONTMAG-CM and by EU-FP7 through NANOPYME Project (No. 310516
Thermoelectric signature of individual skyrmions
We experimentally study the thermoelectrical signature of individual
skyrmions in chiral Pt/Co/Ru multilayers. Using a combination of controlled
nucleation, single skyrmion annihilation, and magnetic field dependent
measurements the thermoelectric signature of individual skyrmions is
characterized. The observed signature is explained by the anomalous Nernst
effect of the skyrmions spin structure. Possible topological contributions to
the observed thermoelectrical signature are discussed. Such thermoelectrical
characterization allows for non-invasive detection and counting of skyrmions
and enables fundamental studies of topological thermoelectric effects on the
nano scal
Light induced decoupling of electronic and magnetic properties in manganites
The strongly correlated material La0.7Sr0.3MnO3 (LSMO) exhibits
metal-to-insulator and magnetic transition near room temperature. Although the
physical properties of LSMO can be manipulated by strain, chemical doping,
temperature, or magnetic field, they often require large external stimuli. To
include additional flexibility and tunability, we developed a hybrid
optoelectronic heterostructure that uses photocarrier injection from cadmium
sulfide (CdS) to an LSMO layer to change its electrical conductivity. LSMO
exhibits no significant optical response, however, the CdS/LSMO
heterostructures show an enhanced conductivity, with ~ 37 % resistance drop, at
the transition temperature under light stimuli. This enhanced conductivity in
response to light is comparable to the effect of a 9 T magnetic field in pure
LSMO. Surprisingly, the optical and magnetic responses of CdS/LSMO
heterostructures are decoupled and exhibit different effects when both stimuli
are applied. This unexpected behavior shows that heterostructuring strongly
correlated oxides may require a new understanding of the coupling of physical
properties across the transitions and provide the means to implement new
functionalities
Emergence of the Stoner-Wohlfarth astroid in thin films at dynamic regime
The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the magnetization reversal of nanoscale systems that are small enough to contain single magnetic domains. However for larger sizes where multi-domain effects are present, e.g., in thin films, this simple macrospin approximation fails and the experimental critical curve, referred as SW astroid, is far from its predictions. Here we show that this discrepancy could vanish also in extended system. We present a detailed angular-dependent study of magnetization reversal dynamics of a thin film with well-defined uniaxial magnetic anisotropy, performed over 9 decades of applied field sweep rate (dH/dt). The angular-dependent properties display a gradual transition from domain wall pinning and motion-like behaviour to a nucleative single-particle one, as dH/dt increases. Remarkably, in the high dynamic regime, where nucleation of reversed domains is the dominant mechanism of the magnetization reversal (nucleative regime), the magnetic properties including the astroid become closer to the ones predicted by SW model. The results also show why the SW model can successfully describe other extended systems that present nucleative regime, even in quasi-static conditionsThis work has been supported by MINECO (Ministerio de Economía y Competitividad)
through Projects No. MAT2012-39308, FIS2015-67287-P, and FIS2016-78591-C3-1-R, by the Comunidad de
Madrid through Project S2013/MIT-2850 NANOFRONTMAG-CM, and by MINECO through the FLAGERA
Programme of Graphene Flagship: SOgraph project (No. PCIN-2015-216); and M-era.Net Programme:
NEXMAG project (PCIN- 2015-126). IMDEA-Nanociencia acknowledges support from the ‘Severo Ochoa’
Program for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). P.P. acknowledges support
through the Marie Curie AMAROUT EU Programme and JCI-2011-09602. A.B. acknowledges MINECO
through the ENMA-National project (MAT2014-56955-R)