Vitaly A. Orlov

On the low-frequency resonance of magnetic vortices in micro- and nanodots

The resonance motion of the magnetization of thin cylindrical and parallelepiped micro- and nanodots has been studied theoretically and experimentally. Analytical expressions for the external-field dependence of the resonance frequency of the vortex-structure oscillations have been derived taking into account the inertial and damping coefficients. The external-field dependence of the damping parameter has been found theoretically. The influence of the effective mass of a magnetic vortex on its low-frequency dynamics has been discussed.

Collective dynamics of magnetic vortices in an array of interacting nanodots

The lift of the degeneracy of the resonance frequency of motion of the core of a magnetic vortex in a square array of nanodots has been experimentally detected. The appearance of a frequency multiplet has been theoretically explained. It has been shown that a reason for the lift of degeneracy can be the magnetostatic interaction between nanodots.

Scenarios of magnetization reversal of thin nanowires

The mechanism of magnetization reversal of a nanowire through the displacement of domain walls and the mechanism of magnetization reversal through the growth of nuclei of the reverse phase have been investigated. It has been found that the displacement of domain walls pinned by magnetic inhomogeneities is similar to the displacement of domain walls in the bulk material, whereas the magnetization reversal by means of the nucleation is fundamentally different. The threshold of the catastrophic growth of a nucleus has been revealed and analyzed. The walls bounding the nucleus have an anomalously low mobility. An explanation of the low mobility of the nucleus boundaries has been proposed.

Mechanisms of Pinning of Domain Walls in Nanowires

Analytical and numerical methods are used to study the process of motion of domain walls in an individual nanowire consisting of ferromagnetic crystallites with a chaotic crystallographic anisotropy. The influence of magnetostatic interaction on the motion is considered. The force profile of the domain wall pinning, caused by stochastic crystallographic anisotropy, is examined. The magnetization curve is analytically constructed and the coercive force is calculated. The Barkhausen jumps of domain walls are investigated. The result is verified by numerically modeling.

Magnetic Structure of Nanowires and Magnetostatic Interaction

The ground state magnetization of nanowires built of ferromagnetic crystallites is considered taking into account the magnetostatic interaction. The criterion of formation of domains is found. The thickness of a domain wall is calculated analytically and the results are compared with the numerical simulations. We show that when the exchange coupling between crystallites is absent its role is played by magnetostatics that ensures the existence of stable domain structure. The direction of the induced anisotropy axis is shown to be determined by the shape of crystallites.

On the Hierarchy of the Characteristic Lengths of Nanowires Magnetization

Using computer simulation of magnetization in a polycrystalline ferromagnetic nanowire, we demonstrate the occurrence of the characteristic spatial scale in the distribution of magnetization unrelated to the domain wall or crystallite size. This is the stochastic domain size. We show that this length not only manifests itself in the analysis of magnetization distribution but is included in the spectral density of the force pinning a domain wall to inhomogeneities of the crystallographic anisotropy. The parameters of a stochastic domain, including the constant and distribution of axes directions of the effective anisotropy, are analytically calculated.