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Subject: Dzyaloshinskii-Moriya interaction ×

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Now showing 1 - 3 of 3
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    Magnetism in curved geometries
    (Bristol : IOP Publ., 2016) Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys
    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.
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    Crossover of skyrmion and helical modulations in noncentrosymmetric ferromagnets
    (Bristol : Institute of Physics Publishing, 2018) Leonov, A.O.; Bogdanov, A.N.
    The coupling between angular (twisting) and longitudinal modulations arising near the ordering temperature of noncentrosymmetric ferromagnets strongly influences the structure of skyrmion states and their evolution in an applied magnetic field. In the precursor states of cubic helimagnets, a continuous transformation of skyrmion lattices into the saturated state is replaced by the first-order processes accompanied by the formation of multidomain states. Recently the effects imposed by dominant longitudinal modulations have been reported in bulk MnSi and FeGe. Similar phenomena can be observed in the precursor regions of cubic helimagnet epilayers and in easy-plane chiral ferromagnets (e.g. in the hexagonal helimagnet CrNb3S6).
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    Curvature effects on phase transitions in chiral magnets
    (Amsterdam : SciPost Foundation, 2020) Yershov, Kostiantyn V.; Kravchuk, Volodymyr P.; Sheka, Denis D.; Rößler, Ulrich K.
    Periodical equilibrium states of magnetization exist in chiral ferromagnetic films, if the constant of antisymmetric exchange (Dzyaloshinskii-Moriya interaction) exceeds some critical value. Here, we demonstrate that this critical value can be significantly modified in curved film. The competition between symmetric and antisymmetric exchange interactions in a curved film can lead to a new type of domain wall which is inclined with respect to the cylinder axis. The wall structure is intermediate between Bloch and N\'eel ones. The exact analytical solutions for phase boundary curves and the new domain wall are obtained.