arXiv subjects

A. V. Chumak

Publications and source records attributed to A. V. Chumak.

44 records · Page 3Linked to original sources

arXiv2009

Current-controlled dynamic magnonic crystal

We demonstrate a current-controlled, dynamic magnonic crystal. It consists of a ferrite film whose internal magnetic field exhibits a periodic, cosine-like variation. The field modulation is created by a direct current flowing through an array of parallel wires placed on top of a spin-wave waveguide. A single, pronounced rejection band in the spin-wave transmission characteristics is formed due to spin-wave scattering from the inhomogeneous magnetic field. With increasing current the rejection band depth and its width increase strongly. The magnonic crystal allows a fast control of its operational characteristics via the applied direct current. Simulations confirm the experimental results.

cond-mat.other↗

arXiv2009

Scattering of surface and volume spin waves in a magnonic crystal

The operational characteristics of a magnonic crystal, which was fabricated as an array of shallow grooves etched on a surface of a magnetic film, were compared for magnetostatic surface spin waves and backward volume magnetostatic spin waves. In both cases the formation of rejection frequency bands was studied as a function of the grooves depth. It has been found that the rejection of the volume wave is considerably larger than of the surface one. The influences of the nonreciprocity of the surface spin waves as well as of the scattering of the lowest volume spin-wave mode into higher thickness volume modes on the rejection efficiency are discussed.

cond-mat.other↗

arXiv2009

Generation of pulse trains by current-controlled magnetic mirrors

The evolution of a spin-wave packet trapped between two direct current-carrying wires placed on the surface of a ferrite film is observed by Brillouin light scattering. The wires act as semi-transparent mirrors confining the packet. Because the spin-wave energy partially passes through these mirrors, trains of spin-wave packets are generated outside the trap. A numerical model of this process is presented and applied to the case when the current in the wires is dynamically controlled. This dynamical control of the mirror reflectivity provides new functionalities interesting for the field of spin-wave logic like that of a spin-wave memory cell.

cond-mat.other↗

arXiv2008

Design and optimization of one-dimensional ferrite-film based magnonic crystals

One-dimensional magnonic crystals have been implemented as gratings of shallow grooves chemically etched into the surface of yttrium-iron garnet films. Scattering of backward volume magnetostatic spin waves from such structures is investigated experimentally and theoretically. Well-defined rejection frequency bands are observed in transmission characteristics of the magnonic crystals. The loss inserted by the gratings and the rejections bands bandwidths are studied as a function of the film thickness, the groove depth, the number of grooves, and the groove width. The experimental data are well described by a theoretical model based on the analogy of a spin-wave film-waveguide with a microwave transmission line. Our study shows that magnonic crystals with required operational characteristics can be engineered by adjusting these geometrical parameters.

cond-mat.other↗

arXiv2008

Bose-Einstein condensation of magnons under incoherent pumping

Bose-Einstein condensation in a gas of magnons pumped by an incoherent pumping source is experimentally studied at room temperature. We demonstrate that the condensation can be achieved in a gas of bosons under conditions of incoherent pumping. Moreover, we show the critical transition point is almost independent of the frequency spectrum of the pumping source and is solely determined by the density of magnons. The electromagnetic power radiated by the magnon condensate was found to scale quadratically with the pumping power, which is in accordance with the theory of Bose-Einstein condensation in magnon gases.

cond-mat.other↗

arXiv2008

Parametrically-stimulated recovery of a microwave signal using standing spin-wave modes of a magnetic film

The phenomenon of storage and parametrically-stimulated recovery of a microwave signal in a ferrite film has been studied both experimentally and theoretically. The microwave signal is stored in the form of standing spin-wave modes existing in the film due to its finite thickness. Signal recovery is performed by means of frequency-selective amplification of one of these standing modes by double- requency parametric pumping process. The time of recovery, as well as the duration and magnitude of the recovered signal, depend on the timing and amplitudes of both the input and pumping pulses. A mean-field theory of the recovery process based on the competitive interaction of the signal-induced standing spin-wave mode and thermal magnons with the parametric pumping field is developed and compared to the experimental data.

cond-mat.other↗

arXiv2008

Scattering of backward spin waves in a one-dimensional magnonic crystal

Scattering of backward volume magnetostatic spin waves from a one-dimensional magnonic crystal, realized by a grating of shallow grooves etched into the surface of an yttrium-iron garnet film, was experimentally studied. Rejection frequency bands were clearly observed. The rejection efficiency and the frequency width of the rejection bands increase with increasing groove depth. A theoretical model based on the analogy of a spin-wave film-waveguide with a microwave transmission line was used to interpret the obtained experimental results.

cond-mat.mtrl-sci↗

arXiv2008

Microwave spectral analysis by means of non-resonant parametric recovery of spin-wave signals in a thin magnetic film

We report on the storage and non-resonant parametric recovery of microwave signals carried by a dipolar surface spin-wave pulse in a thin ferrimagnetic film. The information about the intensity of the spectral components of the signal within a narrow frequency band is saved due to the excitation of a dipolar-exchange standing spin-wave mode across the film thickness and is afterwards restored by means of parametric amplification of this mode. The intensity of the restored signal measured for varying shifts between the signal carrier frequency and half of the pumping frequency, which is equal to the frequency of the standing mode, reveals information about the entire frequency spectrum of the input microwave signal.

cond-mat.mtrl-sci↗