Excitation of Ultrashort Spin Waves via Spin-Cherenkov Effect in Magnetic Waveguides

The excitation of ultrashort wavelength spin waves via the spin-Cherenkov effect in magnetic waveguides is investigated via a micromagnetic modeling. The proposed excitation method is relatively simple and easily tunable. The excitation efficiency of the proposed scheme is obtained for different excitation pulse velocities and widths. A coupled waveguide system is also considered. In this case, the spin waves are excited in the first waveguide and then are transferred to the second one due to the dipolar coupling between waveguides. It is also shown that the excitation and transfer of excited spin waves have some limitations related to the dipolar coupling mechanism between the waveguides.

Латеральный спин-волновой транспорт в системе неидентичных магнонно-кристаллических микроволноводов

The control regimes of dipole coupling in the lateral system of non-identical magnonic crystals are investigated by the method of Mandelstam-Brillouin spectroscopy and by the method of micromagnetic modeling. The modes of spatial and frequency selection of the spin-wave signal near the frequency of the band gap zone of the magnonic crystal are revealed. The influence of changes in geometric parameters on the properties of waveguide modes near the frequency of the Bragg resonance is investigated. The results obtained can be used to create microwave signal processing devices, such as demultiplexers, power dividers, couplers.

Совместное влияние магнитного поля и спин-поляризованного тока на связанную динамику магнитных вихрей в спин-трансферном наноосцилляторе

The joint effect of the spin polarized current and an external magnetic field on the dynamics of magnetization in vortex spin-transfer nano-oscillators with a diameter of 400 nm is investigated. For the numerical calculation of the coupled dynamics of magnetic vortices, the SpinPM software package for micromagnetic modeling was used. The dependence of the frequency of stationary coupled oscillations of vortices on the magnitude of the magnetic field, which determines the operating frequency range of a tunable vortex spin-transfer nano-oscillator.

Частотно-селективное распространение спиновых волн в трехмерном магнонном Т-образном сплиттере

Using numerical and experimental methods, the mechanism of control of the transmission of a spin-wave signal in a three-dimensional magnon splitter, formed by an orthogonal junction of magnetic strips of yttrium iron garnet, has been investigated. It is shown that by variation the size of the air gap between the spin-waveguide sections, it is possible to control the selection of the signal propagating in the output sections of the structure. From an applied point of view, the results obtained can be used to create an interconnection element in multilevel magnon information processing devices for the formation of multilayer magnon network topologies and miniaturization of computing devices based on the principles of magnonics. Key words: spin waves, magnonics, three-dimensional interconnections, micromagnetic modeling.

Micromagnetic Modeling of Magnetite/Maghemite Particles with a Multi-Layer Core-Shelled Structure

Low temperature oxidized core-shelled magnetite is paramount important in recording geomagnetic field. To characterize the effects of transition zone between the core-shell on the magnetic properties of low temperature oxidation of magnetite, micromagnetic models of hysteresis parameters and microstructures of a multi-layer core-shelled model were systematically investigated by MERRILL (Micromagnetic Earth Related Rapid Interpreted Language Laboratory). Numerical simulations indicate that SD particles (<70 nm) remain highly uniform magnetization, but show decreasing coercivities as oxidation preceeds. For fine SV particles (80 nm to 120 nm), the hysteresis parameters respectively increase and dramatic decrease at the early and late stage of oxidation, and the micromagnetic behaviors vary significantly. Finally the hysteresis parameters of larger SV (>130) particles remain nearly unchanged during oxidation. It indicates that fine SV particles are more sensitive to oxidation, and dominate the dramatic change of experiment observation. Overall, low temperature oxidation of magnetite preferring a multi-layer coupled oxidation process from outside to interior and is capable of recording paleomagnetic signals.