Spin valves with a synthetic antiferromagnet were fabricated via magnetron sputtering. It was shown that the fabricated spin valve layers had a perfect microstructure and smooth interfaces, and therefore, an RKKY interaction dominated in the coupling of the ferromagnetic layers separated by a copper spacer. Rhombus-shaped micro-objects were fabricated from a single spin valve film. The thermomagnetic treatment procedure was found to form unidirectional anisotropy in the micro-object such that the values of the exchange bias fields in the rhombus' nonparallel sides were opposite in sign. For the CoFeNi/Ru/CoFeNi synthetic antiferromagnet, we determined the differences between the ferromagnetic layer thicknesses at which the thermomagnetic treatment formed the same exchange bias all over each rhombus' side. We also fabricated a sensor element in which each side of the rhombus was the shoulder of a Wheatstone bridge. After the thermomagnetic treatment procedure, each shoulder worked as an active magnetosensitive element, enabling the device to operate as a full Wheatstone bridge. The sensor output exhibited a step shape, high sensitivity to field changes, and significant magnetic hysteresis. Such characteristics are suitable for switching devices.

The microstructure of the MgB2 core of the single fiber composite consisting of MgB2, the Nb barrier, and the Cu shell (MgB2/Nb,Cu), which is synthesized by the powder-in-tube method with an ex situ option and by subsequent annealing, has been studied. It is shown that a dislocation microstructure that exhibits high thermal stability is formed in the MgB2 core during cold deformation, in addition to powder compaction. A high dislocation density is observed inside MgB2 grains. Dislocations form walls with low misorientation angles between subgrains. Annealing at a temperature of 900°C for 1 h leads to a higher density of MgB2 ceramics, and the intergranular contact area increases. Moreover, MgO inclusions with a size of 10 nm or less are formed. Thus, various kinds of structural defects are formed, which can be considered as probable pinning centers for the magnetic flux.

Secondary phases have been revealed in the course of development of approaches to obtaining the superconducting MgB 2 ceramic. These secondary phases are identified, and the mechanisms of their generation are thoroughly discussed. It is shown that a complex of methods, including the optical microscopy in the polarized light, scanning and transmission electron microscopy, provides opportunities for describing the secondary phases in the MgB 2 ceramic, especially when they cannot be determined only by X-ray analysis.

Transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis have been used to study the structure of superconducting MgB2 ceramics that differ in their contents of alloying elements such as Y and Gd (0.5 and 0.005 wt %). The presence of superfine MgO and Y and Gd boride precipitates was found. The phase composition and sizes of the inclusions and their location in the MgB2 matrix were determined.

The effect of pressure-assisted sintering and preliminary densification by hydrostatic pressure of commercial powder on the microstructure and superconducting properties of MgB 2 ceramics is studied in this work. Various thermomechanical actions are shown to result in the formation of different structural defects, which can be considered probable centers of magnetic flux pinning.

A brief review of synthesis methods of MgB2 and the effect of alloying and thermomechanical treatment on the structure and properties of MgB2 is presented. The review observes the production methods of MgB2-based wires and cables and their applications and perspectives of potential use. Deposition methods of MgB2 films and on the possibility of application of MgB2 films in electronics and for fundamental research in the condensed-matter physics are reported on.

Exchange-biased nanostructures of the “spin valve” type, which include an additional layer of the rare-earth metal dysprosium, are made by magnetron sputtering. Temperature variations in the magnetotransport properties of the spin valves are used as an indicator of change in the magnetic state of the dysprosium nanolayer. Information on the formation of unidirectional magnetic anisotropy at the CoFe/Dy interface upon the transition through Néel temperature of dysprosium is obtained. It is shown that the antiferromagnetic phase in the polycrystalline dysprosium layer has noncollinear magnetic ordering. The temperature dependence of the angle between the directions of the magnetic moments at the dysprosium-layer boundaries is determined. The change in this angle observed in the entire temperature region of the existence of helicoidal ordering in dysprosium reflects the change in the period of the magnetic helicoid in dysprosium with temperature. Thus, a new method for studying chiral magnetics is proposed, in which the indicator of the helicoidal magnetic state is a spin valve possessing giant magnetoresistance, containing a layer of the helimagnet under investigation.

Heterovalent element substitution is an effective way to optimize functional properties of the Y-Ba-Cu-O high-temperature superconductors. In this study, we analyze the effect of Y-Ca substitution on microstructure and critical current in YBa2Cu3O6.8 ceramics with transmission electron microscopy and magnetometry. The obtained results reveal that the substitution of Y3+ by Ca2+ initiates the formation of complicated microstructure consisting of Y(Ca)-123 matrix with multiple defects of different types and fine nanoscale Y-211 particles coherently coupled with the matrix. Depending on Ca doping, various microstructural defects such as dislocations, stacking faults, and effects associated with cationic disorder are observed. The magnetic and superconducting properties in Ca-substituted compositions Y-123 are discussed in terms of the sample microstructure morphology and the specificity of coupling between the basic Y(Ca)-123 phase and impurity particles of the Y-211 phase. We find that shape type and dispersion of the Y-211 precipitations are crucial to regulating both the critical current and the critical temperature in the ceramics.

The fine structure of YBa2Cu3Oy single crystals with a different oxygen content subjected to a low-temperature hydrogenation have been investigated by transmission electron microscopy. It has been shown that as a result of the action of hydrogen at T = 150°С, a partial reduction of copper occurs, accompanied by the precipitation of Cu crystallites of ~100 nm in size and the formation of various structural defects. The geometric configuration of the precipitated crystallites has been considered. The results obtained show that hydrogenation is a method that makes it possible to control the structure by introducing nanosized inclusions and defects, which can be pinning centers of the magnetic vortices.

CoFe-/Cu-based multilayers with two different types of a buffer layer, NiFeCr, and Ta/NiFeCr have been produced by magnetron sputtering. The crystal structure of the superlattice layers has been studied. A correlation between the features of the microstructure and the magnitude of the magnetoresistance has been found. Superlattices with giant magnetoresistive effect reaching up to 83% have been fabricated.

Effects of Cu layer thicknesses and annealing temperature on structural features of Co/Cu superlattices have been studied by nuclear magnetic resonance (NMR), electron microscopy, X-ray diffraction and X-ray reflectometry. Determination of a fraction of perfect boundaries and of Co atoms in interfaces based on NMR studies is demonstrated. Correlation of these parameters with the probability of a single electron scattering event at an interface and magnetoresistance is analyzed.

Spin valves with nanostructure CoFe/Dy/CoFe and three-layer structures metal/Dy/metal were prepared by magnetron sputtering. The measurements of field dependences of magnetoresistance and magnetization were held at different temperatures. The changes of magnetotransport properties of spin valve containing CoFe/Dy/CoFe structure were used for getting information on the magnetic ordering in the dysprosium layer. The characteristic changes of magnetotransport properties caused by the formation of helical ordering in dysprosium layer were detected. Special attention was paid to the estimation of Neel temperature and to the investigation of microstructure of dysprosium nanolayer.

The structure of bulk MgB2 specimens after cold deformation in Bridgeman anvils and “Toroid” chamber and following recovery annealings has been studied by scanning and transmission electron microscopy. It is demonstrated that in spite of the matrix phase grain coarsening by 5-7 times under annealing compared to the as-deformed state, the critical current density increases by a factor of 3 (6.7×104 A/cm2 at 30 K after deformation in the “Toroid” chamber and recovery annealing).