Andrey A. Nikitin

A spin-wave logic gate based on a width-modulated dynamic magnonic crystal

An electric current controlled spin-wave logic gate based on a width-modulated dynamic magnonic crystal is realized. The device utilizes a spin-wave waveguide fabricated from a single-crystal Yttrium Iron Garnet film and two conducting wires attached to the film surface. Application of electric currents to the wires provides a means for dynamic control of the effective geometry of waveguide and results in a suppression of the magnonic band gap. The performance of the magnonic crystal as an AND logic gate is demonstrated.

All-thin-film multilayered multiferroic structures with a slot-line for spin-electromagnetic wave devices

Spin-electromagnetic waves propagating in thin-film multilayered multiferroic structures containing a slot transmission line have been investigated both experimentally and theoretically. The thin-film structure was composed of a ferrite film, a ferroelectric film, and a slot-line. It was shown that the spectrum of the spin-electromagnetic wave was formed as a result of hybridization of the spin wave in the ferrite film with the electromagnetic wave in the slot-line and was electrically and magnetically tunable. For the experimental investigations, a microwave phase shifter based on the multiferroic structure has been fabricated. Performance characteristics are presented.

Theoretical investigation of the resonance properties of an active ring made of a ferrite-ferroelectric layered structure

A theoretical model of a microwave active ring resonator based on a ferrite-ferroelectric layered structure serving as a waveguide for hybrid electromagnetic-spin waves is developed. The resonator is made in the form of a closed ring consisting of a ferrite-ferroelectric delay line, a microwave amplifier, and a variable attenuator. The resonance properties of this system are studied theoretically. The feasibility is demonstrated of effectively controlling the resonance frequencies of the ring by varying the permittivity of the ferroelectric layer.

Dispersion characteristics of spin-electromagnetic waves in planar multiferroic structures

A method of approximate boundary conditions is used to derive dispersion relations for spin-electromagnetic waves (SEWs) propagating in thin ferrite films and in multiferroic layered structures. A high accuracy of this method is proven. It was shown that the spin-electromagnetic wave propagating in the structure composed of a thin ferrite film, a thin ferroelectric film, and a slot transmission line is formed as a result of hybridization of the surface spin wave in the ferrite film and the electromagnetic wave in the slot-line. The structure demonstrates dual electric and magnetic field tunability of the SEW spectrum. The electric field tunability is provided by the thin ferroelectric film. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the slot-line gap width. The theory is confirmed by experimental data.

New Approaches to Electrocaloric-Based Multilayer Cooling

The research and development works directed to a creation of solid state coolers and refrigerators based on the electrocaloric effect have been initiated in various countries, mainly in USA and USSR, in the 70s of the last century The goal of these works was formed as a creation of microcryogenic cooling systems for infrared radiation receivers for space optoelectronic systems.

Theoretical analysis of microwave properties of ferrite-ferroelectric magnonic crystals

Microwave properties of ferrite-ferroelectric magnonic crystals are investigated for the first time. The electric and magnetic rearrangement of the band gaps in the spectrum of proper electromagnetic spin waves in such structures is demonstrated.

Magnetically Tunable Microwave Spin-Wave Photonic Oscillator

A magnetically tunable microwave spin-wave photonic oscillator was designed and modeled. A spin-wave filter made with an yttrium-iron garnet (YIG) film was used simultaneously as a frequency-selective and time-delay element. Frequency tuning of the oscillator was realized in the range of 4-8 GHz through the variation of a bias magnetic field applied to the YIG film. The phase noise was -125 dBc/Hz at 10 kHz offset and -140 dBc/Hz at 100 kHz offset from the oscillation frequency.

Dynamic magnonic crystal based on a layered ferrite–ferroelectric structure

A dynamic magnonic crystal based on a planar multiferroid ferrite–ferroelectric structure is suggested and studied. A space-periodic electric field applied to the ferroelectric layer converts a regular multi-ferroid waveguide to a periodic structure. An electrodynamic model of a dynamic magnonic crystal is constructed, and its dispersion and transfer characteristics are studied.

Electronically tunable spin-wave optoelectronic microwave oscillator

The characteristics of a spin-wave optoelectronic microwave oscillator are experimentally studied for the first time. The oscillator represents a ring structure the microwave circuit of which contains a spinwave delay line based on the yttrium–iron-garnet film. The optical part of the oscillator contains a fiberoptic delay line with a length of 100 m. It is demonstrated that the spin-wave delay line makes it possible to tune the output frequency in wide ranges at a relatively low level of the phase noise. In the gigahertz frequency range, the level of the phase noise is no greater than–110 dBc/Hz at a detuning of 10 kHz from the carrier frequency.

A microwave phase shifter based on a planar ferrite-ferroelectric thin-film structure

Microwave phase shifters employing slot transmission lines based on thin ferroelectric films of barium strontium titanate and thin single-crystalline films of yttrium iron garnet ferrite have been experimentally studied for the first time. The phase shifters admit double electronic control based upon the phenomenon of hybridization of the electromagnetic wave propagating in a slot delay line on the ferroelectric film and the spin wave propagating in the ferrite film. At a bias voltage of 150 V applied to electrodes of the slot lines with 50- and 150-μm-wide slots, the phase shift amounted to 53° and 26°, respectively.