A study of the magnetic properties of synthetic antiferromagnetic nanostructures (SAF) has been carried out. In the SAF structure, two ferromagnetic layers separated by a nonmagnetic metal are coupled by the exchange RKKY interaction (Ruderman— Kittel—Kasuya—Yoshida), which has an oscillating character. The total magnetic moment of the SAF structure is minimal with an antiparallel configuration of the magnetization of the ferromagnetic layers, due to which the effect on the magnetic layers in the structure is reduced. The structures under study have a number of unique properties and are used in the elements of nonvolatile magnetoresistive memory, in magnetic field transducers, and in spin logic devices. The characteristics of the SAF of CoFeB/Ru/CoFe nanostructures with the Ru layer thickness corresponding to the second antiferromagnetic maximum are obtained. The magnetization reversal curves of SAF structures with Ru thickness of 2.1 nm, 2.3 nm and 2.5 nm have been studied. The optimal ratio of ferromagnetic layers was selected to reduce the magnetic moment of the SAF structure. A study of the effect of thermomagnetic treatment on the properties of the SAF nanostructure was carried out, which showed that there are no significant changes in the magnetization reversal, and the magnetic saturation field slightly increases. The curves of magnetization reversal of CoFeB/Ru/CoFe structures fixed by the antiferromagnetic layer are presented. In addition, magnetization reversal curves of spin-tunnel magnetoresistive nanostructures with an antiferromagnetic layer and a SAF structure are presented, and an analysis of the thermal stability of the structures with SAF is also carried out.

A new generation of nonvolatile memory devices are being actively developed and researched. The MRAM test cell is manufactured by Scientific-Manufacturing Complex “Technological Centre.” A control measuring system (CMS) is developed and manufactured for research. The work presents an algorithm for operation of the CMS, which makes it possible to study the spin-tunnel magnetoresistive (STMR) elements of a nonvolatile magnetoresistive random-access memory (MRAM) test cell. The main investigated characteristics of the MRAM test cell are the currents at which the cell is magnetized. Methods for measuring the resistance in a changing magnetic field created by the buses and determining currents for the magnetization reversal of a STMR element are presented in this work. The recording current value of the STMR element for the row is 40 mA and for the column, it is 67 mA. The next stage of the study is writing and reading the STMR elements. The resistance of the STMR element with the “0” logic state is 6.8 kΩ and with the “1” logic state is 13.4 kΩ. The stability of the MRAM element is confirmed by performing switching operations while maintaining the levels of the logic states.

Оптические логические вентили являются перспективными компонентами для построения фотонных схем, выполняющих логические операции и вычисления. Проведено исследование методом конечных разностей во временной области (FDTD) логического вентиля на основе Y-образного волноводного сумматора, выполняющего функции "НЕ", "ИЛИ", "исключающее ИЛИ". По результатам исследования оптимизирована конфигурация Y-образного сумматора, обеспечивающая коэффициент затухания (контрастность) порядка 35,4 дБ между логическими "1" и "0" при времени задержки передачи сигнала на выходной порт 0,33 пс. Рассмотрена возможность реализации каскадной схемы для функции "И-НЕ" с контрастностью порядка 34 дБ и временной задержкой передачи 0,73 пс. Предложенная конструкция логического вентиля потенциально может быть использована при разработке фотонных схем на кристалле для повышения их быстродействия и эффективности.

Представлены результаты исследования экспериментальных образцов и разработанной теоретической модели физического процесса перемагничивания многослойной магниторезистивной наноструктуры с магнитострикционным эффектом. Описаны основные факторы, влияющие на процессы магнитной стрейнтроники. Полученные результаты теоретического расчета магнитосопротивления при механических деформациях согласуются с экспериментальными данными.

Magnetic films of NiFe permalloy and CoNiFe ternary alloy are used in products of nanoelectronics and microelectronics and in densely packed magnetic memory. NiFe and CoNiFe coatings decrease corrosion and wear in electrical devices; they are also used in electrocatalytic materials. Large stresses in magnetic films lead to deformations and the malfunctioning of devices due to peeling of the film from the silicon substrate. In this study, to clarify the nature of the phenomena occurring during the electrochemical deposition of NiFe and CoNiFe films of various thicknesses, which lead to mechanical stresses, investigation of their parameters is carried out. It is demonstrated that measurement of the bending of wafers consisting of Si, SiO 2 , Si 3 N 4 , NiCr, and Ni after the deposition of CoNiFe or NiFe layers on each of them allows determination of the mechanical stresses in the films. It is established that the beinding of the wafers with Si 3 N 4 is negative and greater than that with SiO 2 . The bending after depositing NiCr and Ni layers is negative. The bending of silicon wafers with CoNiFe ternary-alloy films has a maximum value of 180 μm at a film thickness of 12 μm, and that with NiFe films has a maximum value of 150 μm at a film thickness of 15 μm. The bending after depositing NiFe and CoNiFe films is positive. No peeling of the films is observed. The difference in the deformation signs of Ni and CoNiFe or NiFe films and in the direct dependence of the silicon-wafer bending on the thickness of NiFe and CoNiFe films makes it possible to relate the mechanical stresses to hydrogenation (hydrogen embrittlement) and hydrogen release after the process. It is determined that the magnetization of NiFe films is lower than that of triple CoNiFe films. The latter are promising for use in magnetic-field converters.

An exact expression is found for the magnetostatic energy of interaction of a synthetic antiferromagnet with a free layer of a spin-tunnel element and ferromagnetic layers in the shape of strongly oblate ellipsoids of revolution. It is established that the exact value of this energy of interaction can differ considerably from the usual value calculated with the expression for a demagnetizing field. The parameters at which the magnetic interaction of a synthetic antiferromagnet is completely compensated are calculated.

Представлены результаты модельной экспериментальной оценки возможности управления с помощью внешнего термического воздействия интегрально-­оптическим ключом, выполненным в виде кольцевого микрорезонатора с наложенным фазопеременным слоем Ge2Sb2Te5 (GST). Быстрый и обратимый фазовый переход между двумя состояниями – ​аморфным (a-­GST) и кристаллическим (c-­GST) – ​сопровождает большая разность показателей преломления, что может быть использовано в оптических схемах для реализации логических функций.

A theoretical and experimental study of the dependence of the magnetoresistance for two spin-tunnel junctions (STJs) of ellipsoidal shape has been made. The one-sided homogeneous magnetization reversal mode of an ellipsoidal STJ with different aspect ratios has been experimentally selected. Despite the reverse inhomogeneous remagnetization, this selection has allowed for the calculation of the magnetic parameters of these elements by developing the Stoner-Wohlfarth theory.

Представлены основные конструктивно-технологические методы создания интегрально-оптических элементов. Показано, что современные базовые оптические логические элементы («И», «ИЛИ», «И-НЕ», «ИЛИ-НЕ») могут быть реализованы двумя основными методами: на интегрально-оптических структурах, содержащих в своем составе интерферометры Маха-Цендера и микрорезонаторы, и на двумерных фотонных кристаллах. Перечислены основные преимущества и конструктивно-технологические особенности каждого из методов создания интегрально-оптических логических элементов (ИОЛЭ) для создания перспективных фотонных интегральных схем (ФИС).

A flame spray pyrolysis (FSP) technique was applied to obtain pure and Nb(V)-doped nanocrystalline β-Ga2O3, which were further studied as gas sensor materials. The obtained samples were characterized with XRD, XPS, TEM, Raman spectroscopy and BET method. Formation of GaNbO4 phase is observed at high annealing temperatures. Transition of Ga(III) into Ga(I) state during Nb(V) doping prevents donor charge carriers generation and hinders considerable improvement of electrical and gas sensor properties of β-Ga2O3. Superior gas sensor performance of obtained ultrafine materials at lower operating temperatures compared to previously reported thin film Ga2O3 materials is shown.

The change in magnetoresistance upon remagnetization by an external magnetic field is calculated using the model of coherent rotation of the magnetization vector of the free layer of a spin tunnel element subjected to homogeneous strain of tension and compression. It is shown that the conclusions of the theory coincide with the classical experimental.

Results are presented from experimental studies of multilayer periodic Ta/[FeNiCo/CoFe] х /Ta nanostructures to supplement scientific knowledge in the field of magnetic straintronics. The electrophysical parameters of the nanostructures are studied under conditions of controlled mechanical deformation. The effect the number of [FeNiCo/CoFe] periods has on the strength of the magnetoresistive effect is determined experimentally.

The new generation non-volatile memory devices are actively developed and researched. The MRAM test cell was manufactured by the Scientific-Manufacturing Complex "Technological Center". The control measuring system (CMS) was developed and manufactured for research. The article presents an algorithm for the operation of the CMS, which makes it possible to study spin-tunnel magnetoresistive (STMR) elements of a non-volatile MRAM test cell. The main investigated characteristics of the MRAM test cell are the currents at which the cell is magnetized. Methods for measuring resistance in a changing magnetic field created by the buses and determining currents for the magnetization reversal of an STMR element are presented in this article. The recording current of STMR element for the line was 40 mA, for the column was 67 mA. The next stage of the study was writing and reading of the STMR elements. The resistance of the STMR element with "0" logical state is 6,8 Q and with "1" logical state is 13,4 Q. The stability of the MRAM element is confirmed by performing switch operations while maintaining the levels of logical states.

Typical experimental dependences of the giant magnetoresistance of a spin tunnel element are compared to theoretical curves obtained using the classical Stoner–Wohlfarth theory of coherent magnetization reversal and a case of incoherent magnetization reversal with the formation of magnetic domains. It is established that the reversal of magnetization through the formation of a domain structure explains the difference between the experimental hysteretic curve and the Stoner–Wohlfarth theory.

The influence of a magnetic field directed orthogonal to the easy magnetization axis (EMA) of an elliptical spin-tunnel junction based on the Ta/CoFe/CoFeB/MgO/CoFeB/Ru/CoFe/FeMn/Ta structure on the dependence of the spin-tunnel junction (STJ) resistance on the external magnetic field is considered. This dependence is calculated using the model of coherent rotation of the magnetization of the free layer. The calculation results are comparable with the experimental studies and can be used to simulate the design of magnetic field transducers based on spin-tunnel magnetoresistive nanostructures.

Представлены результаты разработки трехосевого магниторезистивного преобразователя слабого магнитного поля (ТОМРП) с нечетной передаточной характеристикой. Изложены особенности конструктивного решения ТОМРП. Приведены результаты испытания ТОМРП в условиях внешних воздействующих факторов (ВВФ).

The results of experimental and theoretical studies of the influence of the current value on the characteristics of anisotropic magnetoresistive magnetic field sensors based on FeNiCo alloy with a "barber-polе" structure are presented. A significant difference was found between the volt-oersted characteristics of the forward and reverse strokes with an increase in the intrinsic current caused by the input supply voltage at sufficiently high external magnetic fields. A theoretical calculation of the volt-oersted characteristic was carried out within the framework of the model of one-dimensional heterogeneity of the magnetization distribution, which coincides with the experimental curves of the forward path.

Представлены результаты исследования влияния шероховатости на добротность оптических резонаторов из SiO2, работающих в режиме мод шепчущей галереи (МШГ). Количественная оценка величины шероховатости профиля резонатора проведена двумя способами - с использованием атомно-силового микроскопа (АСМ) Bruker и растрового электронного микроскопа (РЭМ) Helios 650. На основании полученных экспериментальных данных о шероховатости проведены численные расчеты добротности.

Spin-dependent tunneling structures are widely used in many spintronic devices and sensors. This paper describes the magnetic tunnel junction (MTJ) characteristics caused by the inhomogeneous magnetic field of ferromagnetic layers. The extremely oblate magnetic ellipsoids have been used to mimic these layers. The strong effect of an inhomogeneous magnetic field on the magnetoresistive layers' interaction was demonstrated. The magnetostatic coupling coefficient is also calculated.

The results of the development of a current sensor with galvanic isolation based on the anisotropic magnetoresistive effect without magnetic flux concentrators (MFCs) and two variants of MFC designs are presented. The influence of the MFCs on the electrophysical characteristics of the sensor is studied, as well as their role in the displacement of the conductor relative to the sensitive element. The developed current sensor provides the control of both direct and alternating electric currents with a frequency of up to 210 kHz, starting from 0.5 mA, without breaking the conductor. The range of the measured currents is up to +/- 24 A, with a conversion factor of up to 4 V/A, and the current consumption does not exceed 30 mA in the temperature range from -60 degrees C to +125 degrees C.