Browsing by Author "Leon, Andrea M."

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    Anomalous electronic energy losses in protons passing through Gd thin films
    (2023) Valdes, Jorge E.; Leon, Andrea M.; Arista, Nestor; Esaulov, Vladimir A.
    We report a theoretical analysis of recent data on the unexpectedly high electronic energy loss protons in a polycrystalline gadolinium target. These results led the authors of this data to conclude that the free electron model used to analyse these results fails. In this work we provide a quantitative explanation of the experimental results, using an approach based on density functional theory within the framework of the free electron gas model. We performed semi-classical trajectory simulations (SCTS) and employ the local-density-approximation model (LDA), using an inhomogeneous electron density distribution and the polycrystalline character of Gd samples. The good agreement obtained, delineates the need of considering a realistic description of a particle trajectory and the effective electron density 'seen' along it, whose description remains within a FEG model.
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    Tuning Magnetic Order in CrI3 Bilayers via Moire Patterns
    (2022) Leon, Andrea M.; Velasquez, Ever A.; Caro-Lopera, Francisco; Mejia-Lopez, Jose
    Commensurable twisted bilayers can drastically change the magnetic properties of chromium trihalide layered compounds, which opens novel opportunities for tuning magnetic states through layer rotations. Here, a mathematical approach to obtain moire patterns in twisted hexagonal bilayers by performing a certain commensurable rotation theta over one layer is presented. To test the approach, moire structures with theta=21.79 degrees and 32.20 degrees in the phases R (3) over bar and C2/m of CrI3 are obtained via the related methodology. For comparison purposes, a non-shifted CrI3 structure is also considered. Electronic and magnetic properties of the so-obtained systems are computed by ab initio methodologies. Results show the presence of rotation-angle-dependent magnetic configurations and steep modifications of the dispersion bands due to variations in the nearest and next nearest distances among layers of Cr atoms. Modifications obtained from these commensurable rotations are discussed on the basis of competition among different energy contributions due to changes in the atomic neighborhood.