Low Temperature Physics: 41, 361 (2015); https://doi.org/10.1063/1.4919374
Физика Низких Температур: Том 41, Выпуск 5 (Май 2015), c. 466-481    ( к оглавлению , назад )

Vortex polarity switching in magnets with surface anisotropy

Oleksandr V. Pylypovskyi and Denis D. Sheka

Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine
E-mail: engraver@univ.net.ua

Volodymyr P. Kravchuk and Yuri Gaididei

Bogolyubov Institute for Theoretical Physics of NAS of Ukraine, Kyiv 03680, Ukraine

Received January 21, 2015


Vortex core reversal in magnetic particle is essentially influenced by a surface anisotropy. Under the action of a perpendicular static magnetic field the vortex core undergoes a shape deformation of pillow- or barrel-shaped type, depending on the type of the surface anisotropy. This deformation plays a key point in the switching mechanism: We predict that the vortex polarity switching is accompanied (i) by a linear singularity in case of Heisenberg magnet with bulk anisotropy only and (ii) by a point singularities in case of surface anisotropy or exchange anisotropy. We study in details the switching process using spin-lattice simulations and propose a simple analytical description using a wired core model, which provides an adequate description of the Bloch point statics, its dynamics and the Bloch point mediated switching process. Our analytical predictions are confirmed by spin-lattice simulations for Heisenberg magnet and micromagnetic simulations for nanomagnet with account of a dipolar interaction.

PACS: 75.10.Hk Classical spin models;
PACS: 05.45.–a Nonlinear dynamics and chaos;
PACS: 75.70.Rf Surface magnetism;
PACS: 75.75.–c Magnetic properties of nanostructures;
PACS: 75.78.–n Magnetization dynamics.

Key words: vortex core, surface anisotropy, magnetic field, Heisenberg magnet.

Published online: March 23, 2015