An experimental approach to the problem of the energy distribution of radiation in the THz range created by an electron flow passing through a magnetic junction between thermal and dynamic is considered. The experimental results obtained during the operation of a spin-injection emitter based on an array of heterogeneous magnetic nanowires (NWs) confirmed the assumption about the "competition" of thermal and dynamic radiation processes.

The operation of a spin-injection THz emitter is used to establish the possibility of competition between thermal and spin-injection (dynamic) radiation. It is shown experimentally that raising the intensity of dynamic radiation lowers that of thermal radiation. This is explained by the relationship between dynamic radiation and indirect interband spin-flip transitions accompanied by a change in momentum, and thus the absorption of phonons.

The article presents the results of research of two spin-injection sources of THz radiation using different structures of thin-film magnetic transitions (MT) with antiferromagnetic (AFM) FeMn film of nanoscale thickness and ferromagnetic (FM) Fe layer. In both variants, the possibility of intrinsic magnetization forming in the AFM film under the action of a spin-polarized current of a relatively small value formed in the FM layer is shown. The physical foundations of this effect based on the AFM sublattices beveling by a spin-polarized current due to the sd-exchange interaction of the conduction electrons spins with the spins of d electrons of the FM crystal lattice are considered. This does not require an external magnetic field. sd-exchange mechanism of excitation of intrinsic magnetization in AFM is an alternative to the spin-orbit mechanism, which has been widely considered recently. The relations for calculating the frequency and power of spin-injection radiation are given. New experimental results have been obtained that develop the concept of the AFM's intrinsic magnetization. The non-thermal nature of spin-injection radiation and the possibility of increasing the efficiency of the emitter operation due to the ordering of the MT structure by an external magnetic field are shown. The way of increasing the efficiency of spin-injection emitters by creating structures with multiple independently operating micro-emitters at frequencies close to 16 THz and with a signal power of up to a hundred microwatts has been determined. In general, it is shown that the use of the effect of excitation of intrinsic magnetization in AFM is of interest, both from the point of view of the development of theoretical ideas about the magnetic properties of AFM, and from a practical point of view for the creation of spin-injection lasers (tasers).

AbstractA system of spin-injection emitters employing magnetic junctions based on an array of parallel nanodimensional wires has been studied. Manufacturing technology and possible variants of the nanowire structure are discussed. Conditions of the formation of a new type of spin-injection emitters of terahertz radiation on this basis are considered. The design of the experimental setup is described, and the results of experiments are analyzed. It is established that signals in a 16–18 THz range can be generated by passing high-density current through the proposed nanowire array.

A system of spin-injection emitters employing magnetic junctions based on an array of parallel nanodimensional wires has been studied. Manufacturing technology and possible variants of the nanowire structure are discussed. Conditions of the formation of a new type of spin-injection emitters of terahertz radiation on this basis are considered. The design of the experimental setup is described, and the results of experiments are analyzed. It is established that signals in a 16–18 THz range can be generated by passing high-density current through the proposed nanowire array.

A solid-state self-oscillating system that provides generation of ultra-wideband chaotic signals in the microwave range has been proposed, implemented, and studied. The system has a simple structure comprising an active element (bipolar transistor) and a single reactive element (inductance). An experimental study of bifurcation phenomena and typical oscillation modes in the system has been carried out. The energy efficiency of the system and the possibility of its implementation in the form of a chip structure are analyzed.

Предложена, реализована и исследована твердотельная автоколебательная система, позволяющая получать сверхширокополосные хаотические сигналы в микроволновом диапазоне. Система имеет простую структуру, состоящую из активного элемента (биполярный транзистор) и единственного реактивного элемента (индуктивность). Проведено экспериментальное исследование бифуркационных явлений и типовых колебательных режимов системы. Проанализированы энергоэффективность системы и возможность ее реализации в виде чип-структуры. DOI: 10.21883/PJTF.2017.03.44232.16429

ТЕХНОЛОГИЯ ПРИБОРОСТРОЕНИЯ И ПРОИЗВОДСТВА ЭКБУДК 621

The possibility of generation of terahertz electromagnetic waves by the current in a planar structure composed of metalferromagnetic nanoparticles imbedded into an antiferromagnetic medium, is considered.

Problems of practical application of microwave chaotic signals are discussed. Examples of the use of dynamic chaos in communication systems, including wireless sensor networks, are shown. International standards IEEE, allowing using of UWB microwave chaotic signals in modern communications and wireless monitoring systems, are analyzed.

The paper presents the experimental study results for the ultrawideband microwave oscillator on the chip-elements and Si-Ge transistor. To increase the efficiency modes the passive nonlinear contour is used. It is shown, that the given system forms chaotic oscillations in the given frequency band with efficiency of~ 8 %.

The possibility of resonance absorption in the terahertz range caused by the sd -exchange interaction at the incidence of an electromagnetic wave on a ferromagnetic metal has been predicted. The absorption coefficient has been calculated. It has been shown that the resonance frequency is determined by the magnetization of a ferromagnet and the absorption coefficient additionally depends on the orientation of the magnetization with respect to the plane of polarization of the wave.

Development of the effective sources of ultra wideband signals is stimulated by much interest to ultra wideband communication technologies. Chaotic oscillators can play the role of such sources. In the report, structure of the microwave solid state ring oscillator capable to generate ultra wideband microwave chaotic signal with uniform power spectral density, is proposed. Its evolution from distributed elements implementation to CMOS IC realization is demonstrated in simulation and experimentally. Dynamics of the basic oscillation modes are investigated, the fact of the chaotic generation is shown. It is demonstrated that such oscillators can be used in different wireless communication applications as a compact device for UWB microwave chaotic signal generation with uniform power spectral density in frequency bandwidth up to 5 GHz and integrated output power reaches about 20 mW.

The approach to design of the power-efficient chaotic solid-state oscillators is proposed. Results of schematic simulation and experiments of microwave oscillator layouts made with the use both microstrip and lumped elements are given. It is shown that generators made on the basis of the approach allow generating chaotic oscillations in the given frequency band with efficiency of (15-25) %.

In this work the authors present a thorough experimental study of a practical realization of a complex analog signal transmission system using dynamic chaos. It is demonstrated that the chaotic synchronous response could be used as a basis for the design of secure communication channels. The results presented in this work confirm the possibility of secure wireless communications in RF band, while they allow the authors to analyze in detail the restrictions and problems connected with the quality of synchronization of the transmitter and the receiver of the wireless communication systems. The effect of the perturbing factors on the transmission quality is investigated theoretically. It is shown that the main reason of the transmission’s quality degradation is the chaotic response desynchronization associated with the phenomenon of “on-off” intermittency. It is found that under the effect of the perturbing factors, the level of information signal fed to the transmitter must be increased in order to obtain qualitative information transmission. However, in order to provide secure communication, one must decrease the information signal level. A compromise on these contradictory requirements provides an improvement of the quality of the synchronous chaotic response in the receiver.