Curvature-induced effects in magnetic nanosystems

Curvilinear magnetic objects are in focus of intensive research due to the possibility to obtain new fundamental effects and stabilize topologically non-trivial magnetic textures at the nanoscale [1]. In geometrically-broken magnetic objects all energy functionals, that contains spatial derivatives, e.g. exchange, magnetostatic and intrinsic Dzyaloshinskii-Moriya (DMI) interactions, are reshaping in a way of appearance additional curvature-induced chiral and anisotropy terms. These novel chiral magnetic responses arise in the physical space, by introducing bends and twists to magnetic architectures even of conventional materials. We address both experimentally and theoretically the appearance of curvature-induced exchange effects in parabolic nanostripes with different geometrical parameters [2]. We show that a pinning of transversal domain wall at the parabolic apex is originated due to the presence of local curvature-induced DMI that creates a subsequent pinning potential. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. In its turn, the interplay between the intrinsic and exchange-induced DMI paves the way to a mesoscale DMI, whose symmetry and strength depend both on the geometrical and material parameters [3]. Developing this concept we propose a novel approach towards artificial ME materials with helimagnetic nanohelices embedded in a piezoelectric matrix [4]. By applying an electric field, small geometrical changes of pitch and radius could lead to the phase transition from a homogeneously magnetized state (full average magnetic moment) to a periodical one (zero average magnetic moment). [1] R. Streubel et. al., J. Phys. D: Appl. Phys. 49,363001 (2016). [2] O. Volkov et al.. Phys. Rev. Lett. 123, 077201 (2019). [3] O. Volkov et al., Sci. Rep. 8, 866 (2018). [4] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).