Periodic Reporting for period 2 - MAGicSky (Magnetic Skyrmions for Future Nanospintronic Devices)
Berichtszeitraum: 2016-09-01 bis 2018-08-31
One of our strategic choices in MAGicSky is to tailor the interface-DM interaction to observe by different imaging techniques some isolated skyrmions at RT in magnetic multilayers (MML) by stacking ultra-thin layers of transition metals (Co, Fe) and spin-orbit metals (Pt, Ir, W, Rh…) alternately. The concerted effort made during the first period enabled us to achieve this first challenging objective with the observation by several imaging techniques (STXM, MFM) and on different MML systems such as Pt/Co/Ir or Pt/Co/AlOx multilayers, some magnetic skyrmions at RT. This key advance has generated a large interest and was crucial for the success of MAGicSky as it was a prerequisite for the addressing the other fundamental objectives. Beyond this achievement, a lot of efforts combining experimental results in epitaxial MML systems and theoretical calculations by e.g. first principle calculations, spin dynamics and Monte Carlo simulations have been performed in the second reporting period to evaluate how the important magnetic parameters can be tuned by changing materials and composition to improve and optimize the skyrmion characteristics. One important challenge was notably to better understand and improve their thermal stability while decreasing their size. To this aim, we rely on elaborating samples with multiple repetitions instead of single thin films. The prize to pay for that is that the interlayer dipolar fields then become more important and can strongly modified the skyrmion shape and size. A combination of experiments, numerical simulations and modelling have been done during this period to tackle this issue, for example with the identification of hybrid chiral skyrmions in some cases, and proposed some guidance for the choice of magnetic parameters to eventually obtain ultra-small and mobile skyrmions at RT. Another important issue has been to improve understanding the interaction with defects or pinning centers.
Finally, the consortium has organized an international workshop dedicated to the physics of skyrmions and the potential applications for a new generation of spintronic devices (Skymag 2). It has been held in Paris in the first week of May 2017, that all the feedbacks from the more than 150 participants were excellent. It has been clearly a great opportunity to disseminate the results of MAGicSky to the ever-growing community of colleagues working on skyrmions and more generally spin-orbitronic effects.