A.V. Sadovnikov

Spatial and Temporal Dynamics of Dissipative Parametric Solitons in a Ferromagnetic Film Active Ring Resonator

This paper reports the experimental results of spatial and temporal dynamics research of dissipative parametric solitons generated in a ferromagnetic film active ring resonator. Such dissipative structures are formed through three-wave parametric decay of a magnetostatic surface wave and frequency-time filtering. The spatio-temporal dynamics of dissipative parametric solitons has been investigated using the Brillouin light scattering technique. It is shown that quasi-stationary temporal structures are formed in a ring along a ferromagnetic film and are not observed in a ferromagnetic film, which is not incorporated into the ring.

Splitting of Spin Waves in Strain Reconfigurable Magnonic Stripe

We report on the study of the spin wave (SW) propagation in the magnonic waveguide which consists of an irregular magnetic thin film and a piezoelectric layer. We demonstrate that the use of a finite-width piezoelectric layer on the top of a magnetic waveguide leads to controllable SW splitting. By means of numerical simulation, we demonstrate the functionality of the proposed structure. We show that the switching of SW power is possible due to electric field variation and thus the proposed structure can act as a frequency-selective multichannel SW splitter and multiplexer.

Nonlinear switching of spin waves in the side-coupled magnonic stripes

The development of magnonic micro and nanosized elements leads to the fabrication of functional devices for planar magnonic applications [1–3].

Strain reconfigurable coupling of spin waves in width modulat-ed magnonic crystal waveguide

Recent progress in the magnon-based electronics shows that spin wave (SW) can be used as a signal carrier in the magnonic waveguiding structures operating in the GHz and THz frequency range [1–3].

Atomic-scale surface engineering for enhancement of the Dzyaloshinskii-Moriya Interaction in thin films with 3d-5d(4d) interfaces

An interface between 3d transition metal and 5d(4d) heavy metal (HM) is a host of intriguing spin-related effects desirable for spin-orbitronic applications [1].

Conversion of magnetostatic spin waves propagating through a junction of magnonic waveguides

Wave channeling is an important problem for signal processing systems and communications within both optical and microwave frequency ranges [1-3]. In optics, the propagation path of a light can be controlled e.g. via the total internal reflection or in photonic crystal fibers. Thus, the simplest problem of wave channeling - turning a wave round a corner - is trivial in photonics, which is due to the isotropy of the optical dispersion. In magnonics [4], in contrast, the information carriers are spin waves, which have a strongly anisotropic dispersion. As a result of this, the magnonic group and phase velocities are non-collinear, while the relationship between them depends strongly on the orientation of the magnetization and the strength of the applied magnetic field. In principle, bends could be avoided in architectures in which magnonic waveguides form right angles at the junctions. However, the same anisotropy then poses another problem - that of conversion between the magnetostatic surface spin waves (MSSWs) and backward volume magnetostatic spin waves (BVMSWs), which have their wave vectors perpendicular and parallel to the direction of the magnetization, respectively.

Nanoconstriction-based spin-Hall oscillators

Recent observations of coherent microwave magnetization oscillations driven by pure spin current have provided novel opportunities for the development of active spintronic devices. It was demonstrated that pure spin current produced by the spin-Hall effect (SHE) can be utilized to implement magnetic nano-oscillators that do not require electrical current flows through the active magnetic layer, allowing one to avoid detrimental effects associated with large densities of the electric current in the magnetic layer typical for the traditional spin-transfer torque (STT) spintronic devices. The previously demonstrated spin-Hall nano-oscillators (SHNO) were found to exhibit a relatively large power and small auto-oscillation linewidth at cryogenic temperatures. However, both of these characteristics significantly degrade at increased temperatures. This drawback can be avoided if a single dynamical mode with a significant spatial extent can be selectively excited in an SHNO. One can expect that the auto-oscillation area should depend on the spin injection geometry. However, in practice local injection of spin current leads to the spontaneous formation of the so-called “bullet” auto-oscillation mode, whose spatial dimensions are determined by the nonlinear self-localization effects rather than the spin-current injection area. Here, we demonstrate SHNOs characterized by efficient room-temperature generation of coherent microwave signals, achieved by controlling the auto-oscillation characteristics using magnetic dipolar effects instead of the self-localization.

Band gap control in periodic structure with magnonic crystal and ferroelectric

At present, magnonic crystals (MC), which are micron- or submicron- scale periodic structures formed on the surface of ferromagnetic films (FF), are of great interest to the researchers. The presence of a spatial period results in formation of band gaps in the spectrum of the magnetostatic waves (MSW) propagating in these structures for the wave numbers that satisfy the Bragg resonance condition The appealing feature of the magnonic crystals is that it is possible to control their band gaps with an external magnetic field and to develop tunable devices for microwave frequency data processing. In improving the band gap-control functional capabilities of the MCs, it is of interest to investigate layered multiferroid structures composed of MC on basis ferromagnetic film and ferroelectric (FE). At high values of the dielectric permittivity, which depends on the applied constant electric field, the electromagnetic waves (EMW) in the FE are substantially slowed down. In this case, as it is known, in the FF-FE structure, at frequencies close to the frequency of the phase synchronism between the EMW and MSW, hybrid electromagnetic-spin waves (HEMSW) arise. The values of the phase synchronism frequencies are determined by both the electric and magnetic fields, i.e., a dual control of the characteristics of the HEMSWs excited in these layered structures is possible. This report presents the results of investigation of the mechanisms of formation and control capabilities band gaps in the structure MC-FE. The main distinctions of the band gaps in this structure from those in a single MC have been determined. It is shown that the characteristics of these band gaps can be controlled by the electric and magnetic field.

Application of color image processing and low-coherent optical computer tomography in evaluation of adhesive interfaces of dental restorations

Durability of bonded interfaces between dentin and a polymer material in resin-based composite restorations remains a clinical dentistry challenge. In the present study the evolution of bonded interfaces in biological active environment is estimated in vivo. A novel in vivo method of visual diagnostics that involves digital processing of color images of composite restorations and allows the evaluation of adhesive interface quality over time, has been developed and tested on a group of volunteers. However, the application of the method is limited to the analysis of superficial adhesive interfaces. Low-coherent optical computer tomography (OCT) has been tested as a powerful non-invasive tool for in vivo, in situ clinical diagnostics of adhesive interfaces over time. In the long-term perspective adhesive interface monitoring using standard methods of clinical diagnostics along with colour image analysis and OCT could make it possible to objectivise and prognosticate the clinical longevity of composite resin-based restorations with adhesive interfaces.