Nanocavity-Mediated Fast Magnetic Vortex Core In-Situ Switching by Local Magnetic Field

Fast in situ switching of magnetic vortex core in a ferromagnetic nanodisk assisted by a nanocavity, with diameter comparable to the dimension of a vortex core, is systematically investigated by changing the strength as well as the diameter of the effective circular region of the applied magnetic field. By applying a local magnetic field within a small area at the nanodisk center, fast switching time of about 35 ps is achieved with relatively low field strength (70 mT) which is beneficial for fast data reading and writing. The reason for this phenomenon is that the magnetic spins around the nanocavity is aligned along the cavity wall due to the shape anisotropy when the perpendicular field is applied, which deepens the dip around the vortex core, and thus facilitates the vortex core switching.

Observation of frequency dependent resonances in magnetic vortex core gyration using time-resolved magneto-optical Kerr microscope with pulsed semiconductor laser illumination

Frequency dependent resonance of magnetic vortex core gyration in micrometer sized permalloy squares was observed by time-resolved magneto-optical Kerr microscope using pulsed semiconductor lasers as a light source in stroboscopic method. Uniform and efficient laser illumination was realized by a speckle reducer consisting of an oscillating multimode optical fiber and a microbending mode scrambler. The resonance frequency of the same sized permalloy squares showed a non-uniformity of up to 15%, suggesting the flatness of the underlayer have a strong influence to the gyration motion.

Features in the Resonance Behavior of Magnetization in Arrays of Triangular and Square Nanodots

Collective modes of the gyrotropic motion of a magnetic vortex core in ordered arrays of triangular and square ferromagnetic film nanodots have been theoretically investigated. The dispersion relations have been derived. The dipole–dipole interaction of the magnetic moments of the magnetic vortex cores of elements has been taken into account in the approximation of a small shift from the equilibrium position. It is shown that the effective rigidity of the magnetic subsystem of triangular elements is noticeably higher than that of the subsystem of square elements of the same linear sizes. The potential application of the polygonal film nanodisks as nanoscalpels for noninvasive tumor cell surgery is discussed