The TRR 227 kindly invites you to a special TRR 227 Theory Seminar.
Speaker: Prof. Konstantin Guslienko, Universidad del País Vasco, UPV/EHU, San Sebastián, Spain & IKERBASQUE, the Basque Foundation for Science, Bilbao, Spain
Title: Magnetic skyrmions in ultrathin films and dots: stability and dynamics
Magnetic skyrmion is a kind of topological soliton, a non-trivial inhomogeneous magnetization texture on the nanoscale. Skyrmions can be manipulated by spin polarized currents of extremely low density in comparison with the densities used in traditional spintronics . Recently the individual skyrmions were experimentally obsreved at room temperature in Co/Pt, Ir/Co/Pt etc. ultrathin multilayer structures, including magnetic dots. To achieve efficient manipulation of the nanosized spin textures and implement skyrmion-based spintronic devices, it is essential to understand skyrmion stability and dynamics in restricted geometries.
In this talk, I focus on the skyrmion stability and excitation spectra in ultrathin magnetic films and cylindrical magnetic dots. The skyrmion can be stabilized at room temperature due to an interplay of the isotropic exchange, interface Dzyaloshinskii-Moriya (DMI), perpendicular magnetic anisotropy and magnetostatic interaction. We consider Bloch- and Neel- skyrmions (see Figure) and calculate their stability phase diagrams and dynamics. The chiral DMI induced on the interfaces of heavy metals with ultrathin ferromagnetic layers (0.5-1 nm) is crucial for the Neel skyrmion stabilization. The calculated spin wave eigenfunctions / eigenfrequencies are classified according to the number of nodes of the dynamical magnetization in the radial and azimuthal directions . The low-frequency skyrmion gyrotropic modes are in GHz frequency range and can be exploited in spin-torque nano-oscillators. The skyrmion eigenfrequencies are represented as functions of the skyrmion equilibrium radius, dot radius and the dot magnetic parameters. Recent experiments on magnetic skyrmion stabilization and dynamics in multilayer films and nanodots are discussed.
 A. Fert et al., Nat. Rev. Mater. 2, 17031 (2017).
 M. Mruczkiewicz et al., Phys. Rev. B 95, 094414 (2017).
Nov 28, 2018 | 10:15 AM - 11:15 AM
Seminar Room 1.4.08 - Physics Department - Freie Universität Berlin (Arnimallee 14, 14195 Berlin-Dahlem)