Growth and characterization of high quality functional (Ni-Co-Fe) oxides on Ru(0001)

esis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de Materiales, leída el 09-10-2020En óxidos complejos, la competencia entre los grados de libertad de carga, spin y orbital da lugar a fenómenos físicos de interés, tales como el ferromagnetismo, la ferroelectricidad o la multiferroelectricidad. En este campo, los avances conseguidos en su crecimiento permiten sintetizar de forma controlada hetero estructuras de alta calidad de los mismos, a veces controlando las dimensiones hasta al nivel de capas atómicas individuales. Por último, la obtención de propiedades electrónicas concretas en películas ultrafinas de óxidos abre la puerta a nuevas rutas para explorar funcionalidades nanoelectrónicas para diferentes aplicaciones...The competition of charge, spin and orbital degrees of freedom in complex oxides leads to intriguing physical phenomena, including ferromagnetism, ferroelectricity or multiferroelectricity. The advances in the growth of oxides gives rise to the controlled synthesis of high-quality oxide heterostructures with monolayer-precision. Designing electronic properties in ultrathin oxide films and interfaces opens up routes to explore novel nanoelectronic functionalities for applications...Fac. de Ciencias FísicasTRUEunpu

Qu­antification of propagating and standing surface acoustic waves by stroboscopic X-ray photoemission electron microscopy

The quantification of surface acoustic waves (SAWs) in LiNbO3 piezoelectric crystals by stroboscopic X-ray photoemission electron microscopy (XPEEM), with a temporal smearing below 80 ps and a spatial resolution below 100 nm, is reported. The contrast mechanism is the varying piezoelectric surface potential associated with the SAW phase. Thus, kinetic energy spectra of photoemitted secondary electrons measure directly the SAW electrical amplitude and allow for the quantification of the associated strain. The stroboscopic imaging combined with a deliberate detuning allows resolving and quantifying the respective standing and propagating components of SAWs from a superposition of waves. Furthermore, standing-wave components can also be imaged by low-energy electron microscopy (LEEM). Our method opens the door to studies that quantitatively correlate SAWs excitation with a variety of sample electronic, magnetic and chemical properties

Generation and Imaging of Magnetoacoustic Waves over Millimeter Distances

Using hybrid piezoelectric-magnetic systems we have generated large amplitude magnetization waves mediated by magnetoelasticity with up to 25 degrees variation in the magnetization orientation. We present direct imaging and quantification of both standing and propagating acoustomagnetic waves with different wavelengths, over large distances up to several millimeters in a nickel thin film.The authors acknowledge Jordi Prat of ALBA for his help during experiments. F. M. acknowledges support from the MINECO through Grant No. RYC-2014-16515. F. M., B. C., and R. C. acknowledge support from MINECO through Grants No. SEV-2015-0496 and No. MAT2017- 85232-R. F. M., J. M. H., and N. S. acknowledge funding from MINECO through Grant No. MAT2015-69144-P. We thank Werner Seidel and Sander Rauwerdink from PDI for assistance in the preparation of acoustic delay lines on LiNbO3. L. A. and M. F. acknowledge support from MINECO through RTI2018-095303-B-C53. This project was partially supported by the ALBA in-house research program through Projects No. ALBA-IH2015PEEM and ALBAIH2017PEEM.Peer reviewe

Generation and Imaging of Magnetoacoustic Waves over Millimeter Distances

Using hybrid piezoelectric-magnetic systems we have generated large amplitude magnetization waves mediated by magnetoelasticity with up to 25 degrees variation in the magnetization orientation. We present direct imaging and quantification of both standing and propagating acoustomagnetic waves with different wavelengths, over large distances up to several millimeters in a nickel thin film

Variation in ligamentous laxity in well-functioning total knee arthroplasty is not associated with clinical outcomes or functional ability

BackgroundAround 20% of revision knee arthroplasty procedures are carried out for a diagnosis of instability. Clinical evaluation of instability is primarily through physical stress testing of knee ligamentous laxity and joint space opening. It is assumed that increased knee ligament laxity is associated with instability of the knee and, by association, reduced physical function. The range of knee ligament laxity in asymptomatic patients with total knee arthroplasty has however not been reported, nor has the association with measures of physical outcomes.MethodsPatients who reported being happy with the outcomes of TKA and denied any feelings of knee instability were evaluated at routine follow-up clinicas. Knee ligamentous stability was evaluated seperately by 2 blinded assessors in both coronal and saggital planes. Assessors classified the ligamentous stability as ‘tight’, ‘neutrol’ or ‘loose’. Clinical outcome was evaluated by Oxford Knee Score, patient satisfaction metric, timed performance test, range of motion and lower limb power. Analysis of variance was employed to evaluate variables between groups with post hoc pairwise comparisons.ResultsIn total, 42 patients were evaluated. Mean time since index surgery was 46 (SD 8) months. In the coronal plane, 11 (26.2%) were categorised as ‘tight’, 22 (52.4%) as ‘neutral’ and 9 (21.4%) as ‘loose’. In the sagittal plane, 15 (35.7%) were categorised as ‘tight’, 17 (40.5%) as ‘neutral’ and 10 (23.8%) as ‘loose’. There were no between-group differences in outcomes: Oxford Knee Score, range of motion, lower limb power, timed functional assessment score or in satisfaction response in either plane (p = 0.05).ConclusionsWe found a range of ligamentous laxity in asymptomatic patients satisfied with the outcome of their knee arthroplasty, and no association between knee laxity and physical ability

Tuning the N\'eel temperature in an antiferromagnet: the case of NixCo1-xO microstructures

We show that it is possible to tune the N\'eel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the deposition rates of Co and Ni. The morphology, shape, crystal structure and composition are determined by low-energy electron microscopy and diffraction, and synchrotron-based x-ray absorption spectromicroscopy. The antiferromagnetic order is observed by x-ray magnetic linear dichroism. Antiferromagnetic domains up to micrometer width are observed

Magnetic domains in SrFe12O19/Co hard/soft bilayers

ESRF (The european Synchrotron) User Meeting 2022, 7 - 9 February, 2022 . -- online meeting . -- https://www.esrf.fr/fr/home/events/conferences/2022/user-meeting-2022.html .-- Youtube access: https://www.youtube.com/playlist?list=PLsWatK2_NAmyYnkC-bXhvT70wsYaTmojqThe nature of the magnetic coupling between a SrFe12O19 particle (hard phase) and a Co layer grown on top (soft phase) has been studied by means of photoemission electron microscopy (PEEM) and spatially-resolved x-ray absorption (XAS) and magnetic circular dichroism (XMCD) at CIRCE, ALBA synchrotron (Spain). Our study reveals the soft metallic overlayer presents an in-plane magnetization despite the strong out-of-plane magnetocrystalline anisotropy of the hard platelet. Thus, the two phases show completely uncorrelated magnetic domain patterns. Micromagnetic simulations seem to indicate the degree of exchange-coupling is low or null, although the conditions for rigid coupling are a priori well met