Boris A. Kalinikos

Ferrite-ferroelectric hybrid wave phase shifters

A dual, electric and magnetic field tunable microwave phase shifter based on the propagation of hybrid spin-electromagnetic waves in a ferrite-ferroelectric bilayer is discussed. The bilayer consists of a single-crystal yttrium iron garnet film and a ceramic barium strontium titanate slab. The electrical tunability of the differential phase shift Δφ is achieved through the application of a voltage across barium strontium titanate. An insertion loss of 20dB and a continuously variable Δφ as high as 650° in the frequency range of 4.5–8GHz are measured.

Electric field tunable ferrite-ferroelectric hybrid wave microwave resonators: Experiment and theory

The electric field tuning characteristics of a combined microwave resonator based on ferrite-ferroelectric layered structure have been studied in a wide range of bias magnetic fields. The combined ferrite-ferroelectric resonator was composed of two rectangular resonators fabricated from a ceramic barium strontium titanate (BST) slab and a single-crystal yttrium iron garnet (YIG) film. The in-plane dimensions for the YIG and BST resonators were chosen to be equal in order to maximize the electromagnetic coupling between their main modes and reduce spurious influence of their higher order modes. A tuning range of 100MHz for the resonator frequency was realized at 5GHz through the variation of magnetic permeability and dielectric permittivity of the YIG-BST structure. A theory for the hybrid wave excitations, based on a coupled-mode approach, has been developed and provides good description of the data.

Ferrite-ferroelectric layered structures for electrically and magnetically tunable microwave resonators

It is demonstrated experimentally that a layered structure consisting of ferrite and ferroelectric thin films can be used as an electrically and magnetically tunable microwave resonator. The dual tunability is realized through the application of a bias electric field to the ferroelectric layer (thus changing its dielectric constant), and a bias magnetic field to the ferrite layer. The resonator having central frequency f0≅5GHz and bandwidth Δf=3.5MHz demonstrated a broadband (∼300Δf) tunability through the variation of the bias magnetic field, and a narrow-band (∼2Δf) tunability through the variation of the bias electric field.

Dipole-exchange theory of hybrid electromagnetic-spin waves in layered film structures

A theory has been developed for normal mode electromagnetic-spin waves propagating in metal–dielectric-ferromagnetic-dielectric-metal film structures. Dipole and exchange interactions are taken into account. An arbitrary direction of the internal bias magnetic field is assumed. A dispersion equation for hybrid waves is derived. Effects of varying the dielectric constants of the dielectric layers and the geometry of the layered structure are analyzed for the dispersion characteristics of hybrid waves. The obtained results are applied to layered structures containing ferromagnetic and ferroelectric layers that could be used as waveguiding structures for dual electrically or/and magnetically tunable microwave devices.

Multifunctional nonlinear magnonic devices for microwave signal processing

A multifunctional microwave spin-wave device utilizing a ferrite-film magnonic crystal is reported. A principal of operation of the device is based on a nonlinear frequency shift and a nonlinear damping of the carrier spin waves propagating in the magnonic crystal. The device performs several functions of microwave signal processing, namely, enhancement of signal-to-noise ratio, limiting or suppression of high-power signals, and power-dependent phase shift.

Experimental observation of symmetry-breaking nonlinear modes in an active ring

Solitons are large-amplitude, spatially confined wave packets in nonlinear media. They occur in a wide range of physical systems, such as water surfaces, optical fibres, plasmas, Bose–Einstein condensates and magnetically ordered media. A distinguishing feature of soliton behaviour that is common to all systems, is that they propagate without a change in shape owing to the stabilizing effect of the particular nonlinearity involved. When the propagation path is closed, modes consisting of one or several solitons may rotate around the ring, the topology of which imposes additional constraints on their allowed frequencies and phases. Here we measure the mode spectrum of spin-wave solitons in a nonlinear active ring constructed from a magnetic ferrite film. Several unusual symmetry-breaking soliton-like modes are found, such as ‘Möbius’ solitons, which break the fundamental symmetry of 2π-periodicity in the phase change acquired per loop: a Möbius soliton needs to travel twice around the ring to meet the initial phase condition.

Multifunctional dual-tunable low loss ferrite-ferroelctric heterostructures for microwave devices

Oriented barium ferrite (BaM) and polycrystalline ferroelectric barium strontium titanate (BSTO) layered structures have been fabricated by pulsed laser deposition. The 0.5μm thick BaM layer has a saturation induction of 4kG, a uniaxial effective anisotropy field of 16kOe, and a relatively low ferromagnetic resonance linewidth of about 25Oe, values that are indicative of a high quality film. The dielectric constant of the 0.9μm thick BSTO layer drops by a factor of 2 for an applied voltage of 3V.

Self-generation of bright microwave magnetic envelope soliton trains in ferrite films through frequency filtering

Resonant ring feedback with frequency filtering has been used for the self-generation of bright soliton trains. The solitons were produced from magnetostatic backward volume spin waves propagated in an in-plane magnetized magnetic film delay line as part of the resonant ring structure. The amplitude and phase time profiles, together with the power spectra of the self-generated pulses, confirm their bright soliton nature.

Electrical tuning of dispersion characteristics of surface electromagnetic-spin waves propagating in ferrite-ferroelectric layered structures

Electrical tuning of dispersion characteristics has been studied experimentally for hybrid surface electromagnetic-spin waves propagating perpendicularly to the direction of the static magnetization in tangentially magnetized layered structures containing ferrite and ferroelectric layers. The tuning is realized through the variation of the dielectric constant of the ferroelectric layer by changing the applied electric field. A comparison between experimentally measured and theoretically calculated dispersion characteristics is presented and shows a good agreement.

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.