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Author: Hübner, René × Subject: Spintronics ×

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Now showing 1 - 3 of 3
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    Flexomagnetism and vertically graded Néel temperature of antiferromagnetic Cr2O3 thin films
    ([London] : Nature Publishing Group UK, 2022) Makushko, Pavlo; Kosub, Tobias; Pylypovskyi, Oleksandr V.; Hedrich, Natascha; Li, Jiang; Pashkin, Alexej; Avdoshenko, Stanislav; Hübner, René; Ganss, Fabian; Wolf, Daniel; Lubk, Axel; Liedke, Maciej Oskar; Butterling, Maik; Wagner, Andreas; Wagner, Kai; Shields, Brendan J.; Lehmann, Paul; Veremchuk, Igor; Fassbender, Jürgen; Maletinsky, Patrick; Makarov, Denys
    Antiferromagnetic insulators are a prospective materials platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A magnetomechanical coupling in antiferromagnets offers vast advantages in the control and manipulation of the primary order parameter yet remains largely unexplored. Here, we discover a new member in the family of flexoeffects in thin films of Cr2O3. We demonstrate that a gradient of mechanical strain can impact the magnetic phase transition resulting in the distribution of the Néel temperature along the thickness of a 50-nm-thick film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 μB nm−2. The antiferromagnetic ordering in the inhomogeneously strained films can persist up to 100 °C, rendering Cr2O3 relevant for industrial electronics applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.
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    Purely antiferromagnetic magnetoelectric random access memory
    (London : Nature Publishing Group, 2017) Kosub, Tobias; Kopte, Martin; Hühne, Ruben; Appel, Patrick; Shields, Brendan; Maletinsky, Patrick; Hübner, René; Liedke, Maciej Oskar; Fassbender, Jürgen; Schmidt, Oliver G.; Makarov, Denys
    Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy efficiency. We propose and demonstrate a purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50-fold reduction of the writing threshold compared with ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we demonstrate reliable isothermal switching via gate voltage pulses and all-electric readout at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed for readout, allowing permanent magnets to be used. Based on our prototypes, we construct a comprehensive model of the magnetoelectric selection mechanisms in thin films of magnetoelectric antiferromagnets, revealing misfit induced ferrimagnetism as an important factor. Beyond memory applications, the AF-MERAM concept introduces a general all-electric interface for antiferromagnets and should find wide applicability in antiferromagnetic spintronics.
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    Structure-property relationship of Co 2 MnSi thin films in response to He + -irradiation
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2019) Hammerath, Franziska; Bali, Rantej; Hübner, René; Brandt, Mira R. D.; Rodan, Steven; Potzger, Kay; Böttger, Roman; Sakuraba, Yuya; Wurmehl, Sabine
    We investigated the structure-property relationship of Co2MnSi Heusler thin films upon the irradiation with He+ ions. The variation of the crystal structure with increasing ion fluence has been probed using nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM), and associated with the corresponding changes of the magnetic behavior. A decrease of both the structural order and the moment in saturation is observed. Specifically, we detect a direct transition from a highly L21-ordered to a fully A2-disordered structure type and quantify the evolution of the A2 structural contribution as a function of ion fluence. Complementary TEM analysis reveals a spatially-resolved distribution of the L21 and A2 phases showing that the A2 disorder starts at the upper part of the films. The structural degradation in turn leads to a decreasing magnetic moment in saturation in response to the increasing fluence.