Denis D. Sheka

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Modifying the curvature in magnetic nanostructures is a novel and elegant way toward tailoring physical phenomena at the nanoscale, allowing one to overcome limitations apparent in planar counterparts. Here, we address curvature-driven changes of static magnetic properties in cylindrically curved magnetic segments with different radii of curvature. The(More)
A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal(More)
The spin-transfer effect is investigated for the vortex state of a magnetic nanodot. A spin current is shown to act similarly to an effective magnetic field perpendicular to the nanodot. Then a vortex with magnetization (polarity) parallel to the current polarization is energetically favorable. Following a simple energy analysis and using direct(More)
We found resonantly excited precession motions of a three-dimensional vortex core in soft magnetic nanospheres and controllable precession frequency with the sphere diameter 2R, as studied by micromagnetic numerical and analytical calculations. The precession angular frequency for an applied static field HDC is given as ωMV = γeffHDC, where γeff = γ〈mΓ〉 is(More)
In 1949 Levinson [1] established one of the most beautiful results of the scattering theory: the Levinson theorem sets up a relation between the number of bound states N l in a given l-th partial wave and the phase shift δl(k), namely δl(0)− δl(∞) = πN l . Ten years later, in 1959, Aharonov and Bohm [2] discovered the global properties of the magnetic flux.(More)
Franz G. Mertens Physikalisches Institut, Universität Bayreuth, D–95440 Bayreuth, Germany (Dated: November 11, 2002) Abstract The Levinson theorem for two–dimensional scattering is generalized for potentials with inverse square singularities. By this theorem, the number of bound states in a given m–th partial wave is related to the phase shift and the(More)
The ground state of the ring–shape magnetic nanoparticle is studied. Depending on the geometrical and magnetic parameters of the nanoring, there exist different magnetisation configurations (magnetic phases): two phases with homogeneous magnetisation (easy–axis and easy–plane phases) and two inhomogeneous (planar vortex phase and out–of–plane one). The(More)
Dynamical topological solitons are studied in classical two–dimensional Heisenberg easy–axis ferromagnets. The properties of such solitons are treated both analytically in the continuum limit and numerically by spin dynamics simulations of the discrete system. Excitation of internal mode causes orbital motion. This is confirmed by simulations. Submitted to:(More)
We study magnon modes in the presence of a vortex in a circular easy–plane ferromagnet. The problem of vortex–magnon scattering is investigated for partial modes with different values of the azimuthal quantum number m over a wide range of wave numbers. The analysis was done by combining analytical and numerical calculations in the continuum limit with(More)