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The rationale for the present study is explained by a high risk of the development of side effects, including nephrotoxic, in patients that receive the treatment with cytostatics bleocin, lastet, and cisplatin for oncologic diseases. The present article focuses on the evaluation of the toxicity of the mentioned drugs. The method of plasma-free renal tissue cultures in mice on the perforated millipore filters was used. The identification of the toxicity of different doses of the drugs was performed by the comparison of the areas of the grown colonies. The authors presented the data that the inhibition of the growth of renal tissue cultures (by 50%) required a 4.3-fold increase in the dose of lastet in comparison with bleocin. The inhibition of the tissue culture colony growth with cisplatin by 85% was registered in the dose of the drug that corresponded to a 3% solution. The materials of the article have significant practical value because a rational indication of cytostatics bleocin, lastet, and cisplatin with regard to their nephrotoxic effect will allow the specialists to improve the treatment outcome and will contribute to the improvement of the quality of life of patients.

Influence of manganese substitution with 3d-ions on the structure, defectiveness, microstructure as well as resistive, dielectric and magnetoresistive properties of single-phase nonstoichiometric La0.6Sr0.15Bi0.15Mn1.1-xBxO3-δ (B = Cr, Fe, Co, Ni) compositions have been studied. All compositions demonstrate slight lattice parameter change of rhombohedral R 3 ¯ c distorted perovskite structure. The molar formulas of a real perovskite structure have been determined. The real structure is defect and contains cation V(c) and anion V(a) vacancies. The resistivity ρ increases with increase of x for all compositions. There is no “metal-semiconductor” phase transition at temperature Тms for x ≥ 0.20. It has been shown that the composition with B = Cr has the highest relative permittivity at x = 0.3. For the first time, the electron-phonon interaction constant γph has been determined for all the compositions within the framework of small polaron hopping model and it has been found that the strongest change of functional properties is a characteristic of the compositions with B = Fe, for which γph takes the maximum value γph ≈ 7.7.

The aim was to define the quality peculiarities of the equilibrium function, the strategy of the body position maintenance and the sensory organization of postural control in women 55-64 years with the risk of geriatric syndrome of falls (GF) development. Methods. 88 women aged 55-64 years (mean age 60.2 ± 3.2 years) were examined. The first group, the study group (SG), included 44 women who reported that experienced two or more falls in the last 8 months, which should be considered as having a risk of GF developing. The second group, the comparison group, randomly included 44 women of the same age who had not experienced a single fall in the last 12 months (postural stability). To assess the components of postural control, the Sensory Organization Test (SOT) of the computer dynamic posturographic complex «Smart Equitest Balance Manager» was conducted. Results. When analyzing SOT parameters, it was found that women in the SG had a quality decrease of the equilibrium function and the strategy of maintaining the body position in all functional tests, as well as their final grade of the entire test, the participation degree of somatosensorial, visual and vestibular information in the balance monitoring. The most important changes in the SOT parameters that affect the majority of the surveyed women in the SG are reflected in a significant decrease in the quality of the equilibrium function in functional tests 3, 5, 6, and in the final grade of the quality of the equilibrium function in SOT, as well as in the degree of involvement of vestibular information in the balance monitoring, what allows to consider these changes as primary predictors of the development of GF in women aged 55-64 years. Conclusion. The significant decrease of the SOT indicators in women aged 55-64 years with the risk of development of GF was detected. It allows to calculate the regulatory parameters of SOT in order to improve the quality of diagnosis of postural changes and the risk of falls.

The article presents the research results of a regulatory profile of cardiac rhythm in a situation of examination, depending on the level of personal and state anxiety. In order to identify the characteristics of a psychosomatic response to the situation of examination stress the level of anxiety was assessed, which made the basis for ranking groups (low-, moderate-, high - anxious cadets). Cardiac rhythm variability was investigated by the method of R. M. Baevsky, and the statistical and spectral analysis was estimated. The study involved 42 apparently healthy cadets of the first course, 35 girls and 7 boys. The average age was (17.5 ± 0.5) years. A cross-sectional (transverse) study was carried out which protocol included 2 stages: the first stage: anxiety level was determined before the exam, functioning parameters of cardiovascular system and cardiac rhythm variability were registered. The second stage: registration of above mentioned parameters immediately after the examination. The analysis of the research results showed that the level of state anxiety before the exam in all groups was above the level of trait anxiety, which was seen as a natural reaction to the situation of the examination. The reaction of the cardiovascular system and the mechanisms of the autonomic regulation of heart rhythm in a standard situation such as examination were provocative depending on the level of anxiety. Highly anxious examinees showed a higher activation of sympathetic part of autonomic division of nervous system which indicated the generalization of anxiety and possibilities of its somatization.

The structure, its defects, nanostructural clustering and functional properties of the La0.7Ca0.3-xKxMn1+xO3-δ ceramic with x = 0–0.3 have been investigated by x-ray diffraction, thermogravimetric, SEM, resistance, magnetic, magnetoresistance and dielectric spectroscopy methods. We establish that the lattice parameter of the cubic structure increases when the Ca2+ ions are substituted with ions of K+. We show that the real perovskite structure contains different valence states of manganese MnA2+,MnB3+ and MnB4+ in A- and B-positions, as well as vacancy type point defects, in the form of anionic V(a) and cationic V(c) vacancies. The increase in the content of the superstoichiometric manganese is connected to the nanostructured clustering process. We find that K+ and superstoichiometric manganese cause the increase in relative permittivity e′ and dielectric loss tangent angle tg δ. The experimental phase diagram of the magnetic state has been constructed and allows determining the composition of the magneto...

The structure, the structure imperfection, and the magnetoresistance, magnetotransport, and microstructure properties of rare-earth perovskite La0.3Ln0.3Sr0.3Mn1.1O3–δ manganites are studied by X-ray diffraction, thermogravimetry, electrical resistivity measurement, magnetic, 55Mn NMR, magnetoresistance measurement, and scanning electron microscopy. It is found that the structure imperfection increases, and the symmetry of a rhombohedrally distorted R3c perovskite structure changes into its pseudocubic type during isovalent substitution for Ln = La3+, Pr3+, Nd3+, Sm3+, or Eu3+ when the ionic radius of an A cation decreases. Defect molar formulas are determined for a real perovskite structure, which contains anion and cation vacancies. The decrease in the temperatures of the metal–semiconductor (T ms) and ferromagnet–paramagnet (T C) phase transitions and the increase in electrical resistivity ρ and activation energy E a with increasing serial number of Ln are caused by an increase in the concentration of vacancy point defects, which weaken the double exchange 3d 4(Mn3+)–2p 6(O2–)–3d 3(Mn4+)–V (a)–3d 4(Mn3+). The crystal structure of the compositions with Ln = La contains nanostructured planar clusters, which induce an anomalous magnetic hysteresis at T = 77 K. Broad and asymmetric 55Mn NMR spectra support the high-frequency electronic double exchange Mn3+(3d 4) ↔ O2–(2p 6) ↔ Mn4+(3d 3) and indicate a heterogeneous surrounding of manganese by other ions and vacancies. A correlation is revealed between the tunneling magnetoresistance effect and the crystallite size. A composition–structure imperfection–property experimental phase diagram is plotted. This diagram supports the conclusion about a strong influence of structure imperfection on the formation of the magnetic, magnetotransport, and magnetoresistance properties of rare-earth perovskite manganites.

Structure and its defects, magnetic resonance and magneto-transport properties of La0.6–xEuxSr0.3Mn1.1O3–δ magnetoresistive ceramics were investigated by x-ray diffraction, thermogravimetric, resistance, magnetic, 55Mn NMR and magnetoresistance methods. It was found that isovalent substitution of lanthanum by europium A-cation of a smaller ionic radius increases the structural imperfection and leads to a symmetry change from the rhombohedrally distorted perovskite structure of R 3 ¯ c symmetry to the pseudocubic type. It was shown that the real structure contains anionic and cationic vacancies, the concentrations of which increases with the Eu concentration and the sintering temperature tann. A decrease in the temperature of the metal–semiconductor Tms and ferromagnetic–paramagnetic TC phase transitions as well as an increase in the resistivity ρ and the activation energy Ea with increasing x are due to an increase in vacancy concentration, which weakens the high-frequency electron double exchange Mn3+ ↔ ...

X-ray diffraction, magnetic, transport and SEM measurements were used to investigate the role of structural and magnetic inhomogeneities in the formation of magneto-transport properties of the La0.6−xSmxSr0.3Mn1.1O3−δ (x=0–0.6) ceramics. Reduction of the a parameter of perovskite structure and change of its symmetry are shown to be due to both replacement of La3+ by Sm3+ and an increase concentration of anion and cation vacancies. Broad asymmetric 55Mn NMR spectra are indicative of the high frequency electron double exchange Mn3+↔Mn4+ and demonstrate the heterogeneity of magnetic and valence Mn-states. An excess manganese is dissolved in perovskite structure statistically without formation of planar antiferromagnetic clusters of Mn2+ ions in the deformed A positions. Constructing phase diagram of “composition–structure–properties” describes a strong correlation between structural, resistive and magnetic properties as well as reflects a special role of structural defects in the formation of magneto-transport properties of the rare-earth manganites.

Nanopowder La 0.6 Sr 0.3 Mn 1.1 O 3−δ compacts by the oxide-salt, co-precipitation and atomization hydrolysis technologies have been obtained. Structure and its defects, average particle size and functional properties of the nanopowder compacts by X-ray diffraction, thermogravimetric, resistance, magnetic, 55Mn NMR, magnetoresistance and BET methods have been investigated. Connections between the dispersion of nanopowders and their structural, magnetic, resistance, magnetoresistance and baroresistance properties have been established. Broad and asymmetric 55Mn NMR spectra testify the high-frequency electron double exchange Mn3+↔O2−↔Mn4+ and indicate inhomogeneous environment of Mn by other ions and vacancies. The increase in high hydrostatic pressure up to 1.6 GPa leads to decrease in resistivity and activation energy as well as raise in density, coercive force, magnetoresistance and baroresistance effects of the nanopowder compacts.

The influence of substitution of Fe ions for manganese on the structure, phase transitions, magnetoresistance, 55 Mn NMR and 57 Fe Mossbauer spectra in the ceramic La 0.6 Sr 0.3 Mn 1.1 − x Fe x O 3 ( x =0–0.15) samples has been studied by X-ray diffraction, electron microscopy, magnetic, 55 Mn NMR and 57 Fe Mossbauer methods. The real rhombohedral perovskite structure ( R 3 ¯ c ) is established to contain the different valence manganese ions (Mn 3+ and Mn 4+ ), anion and cation vacancies as well as nanostructural clusters with Mn 2+ located in the A-sites. Temperature dependences of the a lattice parameter, a ( T ), demonstrate the anomalies near the Curie temperature, T c . Wide asymmetric 55 Mn NMR spectra confirm the high frequency electron double exchange between Mn 3+ and Mn 4+ ions and irregularity of their surrounding by other ions and defects. According to the Mossbauer spectroscopy data, Fe 3+ ions ( ~ 80 % ) substitute for Mn 3+ and partially Mn 4+ in the B-positions. The rest of Fe 3+ (Fe 2+ ) ions and clusters with Mn 2+ are located in the A-positions. The temperatures of metal–semiconductor and ferromagnet–paramagnet phase transitions are reduced with increasing x , and the magnetic irregularity increases due to the weakening high-frequency Mn 3+ ↔Mn 4+ double exchange by Fe 3+ ions. The amount of ferromagnetic phase is also reduced. The anomalous hysteresis is interpreted as a result of anisotropy of exchange interaction between the ferromagnetic matrix and antiferromagnetic cluster containing Mn A 2 + ions. The phase diagram demonstrates the strong correlated interrelation among magnetic, transport and magnetoresistance properties.

Ceramic samples of Pr0.6−xNdxSr0.3Mn1.1O3−δ (x = 0−0.6) were studied by x-ray diffraction, resistive, magnetic (χac and 55Mn NMR), magnetoresistive and electron microscopy methods. It was shown that with increasing the concentration x, the type of unit cell distortion changes from orthorhombic (x = 0–0.2) to pseudo-cubic (x = 0.4–0.6), and the imperfection of the structure, which contains anion and cation vacancies, is increased. A decrease in the temperatures of metal–semiconductor (Tms) and ferromagnetic–paramagnetic (TC) phase transitions and an increase in the resistivity and activation energy with increasing x was explained by an increase in the concentration of vacancies, which weakens high-frequency electronic double-exchange Mn3+ ↔ Mn4+. It was found that the compositions with a higher content of neodymium exhibit a transition to the antiferromagnetic state at temperatures below 130 K. Two types of magnetoresistive effects were observed. The magnitude of the first effect, which occurs near the pha...

X-ray powder diffraction, resistance, magnetic susceptibility, magnetization, nuclear magnetic resonance (NMR) and magnetoresistance measurement methods were used to study the influence of excess manganese on structure defects and functional properties of (Nd0.7Sr0.3)1−xMn1+xO3 ceramics annealed at 1200 and 1500 °C. It was established that, with an increase in both excess manganese and annealing temperature, the perovskite structure defects, resistance and activation energy increase, while the magnetic susceptibility and fraction of ferromagnetic phase decrease. The occurrence of nanostructured planar clusters is shown to be caused by the presence of excess manganese. Broad asymmetric 55Mn NMR spectra are indicative of both the high-frequency electron Mn3+ ↔ Mn4+ exchange and the uneven distribution of ions and vacancies. The magnetoresistance effect near the Curie temperature increases with increasing annealing temperature and excess manganese content. Magnetic phase diagrams characterizing a strong correlation between the composition, structural defects and functional properties in manganese–neodymium perovskites were constructed.

The structure, lattice imperfection, and properties of ceramic samples La0.6 − x Nd x Sr0.3Mn1.1O3-δ (x = 0–0.4) have been investigated using the X-ray diffraction, resistive, magnetic (χac, 55Mn NMR), magnetoresistive and microscopic methods. It has been shown that there is a satisfactory agreement between the concentration decrease in the lattice parameters a of the rhombohedral (x = 0, 0.1, 0.2) and cubic (x = 0.3, 0.4) perovskite structures and the average ionic radii $$\bar R$$ for the lattice containing anion vacancies, cation vacancies, and nanostructured clusters with Mn2+ ions in A-positions. With an increase in the neodymium concentration x, the vacancy-type imperfection increases, the cluster-type imperfection decreases, the temperatures of metal-semiconductor phase transition T ms and ferromagnetic-paramagnetic phase transition T C decrease, and the content of the ferromagnetic phase decreases. The anomalous hysteresis is associated with the appearance of unidirectional exchange anisotropy induced in a clustered perovskite structure consisting of a ferromagnetic matrix and a planar antiferromagnetic cluster coherently coupled with it. An analysis of the asymmetrically broadened 55Mn NMR spectra has revealed a high-frequency electronic double exchange (Mn3+-O2−-Mn4+) ↔ (Mn4+-O2−-Mn3+) and an inhomogeneity of the magnetic and charge states of manganese due to the heterogeneous environment of the manganese ions by other ions and defects. The observed changes in the resonant frequency and width of the resonance curve are caused by changes in the ratio Mn3+/Mn4+ and magnetic inhomogeneity. An increase in the neodymium concentration x leads to a decrease in the ferromagnetic phase content determined from the dependences 4πNχac(T) and the 55Mn NMR curves. The phase diagram characterizes an interrelation between the composition, the imperfection of the structure, and the transport, magnetic, and magnetoresistive properties of lanthanum neodymium manganite perovskites. It has been found that there is a correlation between the imperfection, magnetic inhomogeneity, coercive force, and magnetoresistance effect exhibited by the perovskite structure.

Detailed studies of manganese zinc ferrites for electronic applications are used to assess the effect of oxygen nonstoichiometry on their structural, electrical, and magnetic properties. The optimal synthesis conditions and nonstoichiometry are determined which ensure the preparation of high-permeability manganese zinc ferrites with low electromagnetic energy losses. The manganese zinc ferrites are shown to be attractive as materials for high-performance magnetoresistive electric current and magnetic field sensors and spintronic devices.

With the goal to establish a direct effect on resiliency of organisms’ cells, there was studied the effect of garlic preparation Phytoncidin on growth of mice’ kidney tissue cells in their cultivation in growth medium 199 with fetal serum and without it. It has been established that in the set span of concentrations, Phytoncidin delayed formation of cell colonies and their growth all the way to a complete stop of their formation.

Ceramic samples of lanthanum strontium manganite perovskites La0.6Sr0.2Mn1.2 − xNbxO3 (x = 0–0.3) annealed at temperatures of 1260 and 1500°C have been investigated using the X-ray diffraction, electron microscopic, resistive, magnetoresistive, and magnetic (χac, 55Mn NMR) methods. It has been found that there is a correlation between the increasing unit cell parameter a of the rhombohedral R\(\bar 3\)c structure and the average ionic radius with increasing niobium concentration x and annealing temperature for the case where the lattice contains anion vacancies, cation vacancies, and nanostructured clusters. The observed increase in the electrical resistivity and decrease in the temperatures of metal-semiconductor phase transition Tms and ferromagnetic-paramagnetic phase transition TC with an increase in the niobium concentration x and the annealing temperature have been explained by the decrease in the content of the ferromagnetic phase, as well as by changes in the ratio Mn3+/Mn4+, the oxygen nonstoichiometry, and the concentration of defects weakening the high-frequency electronic exchange of the ions Mn3+ ↔ Mn4+. The presence of nanostructured clusters in the lattice has been confirmed by an anomalous hysteresis associated with the unidirectional exchange anisotropy of the interaction between the ferromagnetic matrix and antiferromagnetic clusters with Mn2+ and Nb3+ in distorted A-positions. An analysis of the asymmetrically broadened 55Mn NMR spectra and their computer decomposition have revealed a high-frequency electronic exchange and an inhomogeneity of the magnetic and valence states of manganese due to the nonuniform distribution of all ions and defects. Two types of magnetoresistive effects have been found: one effect, which is observed near the phase transition temperatures TC and Tms, is caused by scattering at intracrystalline nanostructured heterogeneities of the imperfect perovskite structure, and the other effect, which is observed in the low-temperature range, is induced by tunneling through intercrystalline mesostructured boundaries. The phase diagram has demonstrated that there is a strong correlation between the composition, structure, resistive and magnetic properties of rare-earth manganites.

Ceramic samples of manganite perovskites La0.6 − xPrxSr0.3Mn1.1O3 (x = 0−0.6) have been studied using the X-ray diffraction, resistive, magnetic (χac, 55Mn NMR), microscopic, and magnetoresistive methods. It has been found that an increase in the praseodymium concentration x leads to a transition from the rhombohedral R\(\bar 3\)c (x = 0–0.3) to orthorhombic Pbnm (x = 0.4–0.6) perovskite structure. It has been shown that the real perovskite structure contains anion and cation vacancies, whose concentrations increase with an increase in the praseodymium concentration x. A decrease in the metal-insulator phase transition temperature Tmi and the ferromagnetic-paramagnetic phase transition temperature Tc with increasing x correlates with an increase in the concentration of vacancies weakening the high-frequency electronic exchange Mn3+ ↔ Mn4+. For compositions with x = 0 and 0.1, when the lattice contains not only vacancies but also nanostructured clusters with Mn2+ in the A-positions, there is an anomalous hysteresis. An analysis of the asymmetrically broadened 55Mn NMR spectra of the compounds has revealed a high-frequency electronic exchange of the ions Mn3+ Mn4+ in the B-positions and a local heterogeneity of their surrounding by other ions (La2+, Pr3+, Sr2+) and vacancies. The phase diagram has demonstrated that there is a strong correlation between the composition, imperfection of the perovskite structure, phase transition temperatures Tmi and Tc, and magnetoresistive properties.

The structural, resistive, magnetic, and magnetoresistive properties of the La0.6Sr0.3 − xBixMn1.1O3 ceramics have been studied. The substitution of Bi ions for Sr ions increases the lattice parameter of the rhombohedral perovskite structure, decreases the metal-semiconductor and ferromagnet-paramagnet phase transition temperatures and the peak of the magnetoresistive effect, and increases the resistivity, approaching the system to the ferroelectric state. The 55Mn NVR study indicates on the high-frequency Mn3+ ↔ Mn4+ superexchange and heterogeneity of the valence and magnetic states of manganese due to the nonuniformity of distribution of all ions and defects. The phase diagram has been constructed, which shows a strong correlation between the structural, magnetic, and magnetoresistive properties.

Ceramic (La0.7Ca0.3)1 − x Mn1 + x O3 samples are studied by X-ray diffraction, resistive, magnetic, 55Mn NMR, and magnetoresistance methods. The concentration changes of lattice parameter a of the cubic perovskite structure and its average ionic radius are in good agreement if the concentrations of anion and cation vacancies and nanostructured clusters with Mn2+ in the A positions increase with x. Phase transition temperatures T ms and T c weakly depend on x, and the electrical resistivity and the activation energy decrease substantially with increasing x due to a change in the imperfection of the perovskite structure. An analysis of the broad asymmetric 55Mn NMR spectra of the samples indicate a high-frequency Mn3+↔ Mn4+ electron superexchange and nonuniform magnetic and valence states of these ions because of a nonuniform distribution of ions and defects, which decrease the amplitude resonance frequency with increasing x. The magnetoresistive (MR) effect near phase-transition temperatures T ms and T c increases substantially with x and is caused by the effect of a magnetic field on the scattering of charge carriers by intracrystallite nanostructured heterogeneities of an imperfect perovskite structure. The second MR effect is located in the low-temperature range, is related to tunneling through mesostructural crystallite boundaries, and decreases weakly with increasing x. A correlation is found between the hyperstoichiometric manganese content, the imperfection of the perovskite structure, and the magnitude of the MR effect.

Types of orientation to interaction and kinds of perception of a group in second-year students of a medical higher educational institution have been studied. It has been established that the type of perception of the group was mostly affected by the education level, the kind of orientation to interaction was affected by education success. Among the students, there prevailed the pragmatic type of perception of the group; at the Faculty of Dentistry, most students had dominating individualistic motivations. The collectivistic type of perception of the group was characteristic of the low-successful students. Orientation to a task prevailed in the students with medical and non-medical vocational secondary education.

The La0.7Pb0.3 − x Sn x MnO3 composition ceramic is studied by X-ray diffraction, resistive, magnetic, electron-microscopic, magnetoresistance, and NMR (55Mn, 139La) methods. The substitution of tin for lead results in structural phase separation into the basic perovskite ( $R\bar 3c$ ) and spinell (Fd3m), phases: La0.7Pb0.3 − x Sn x MnO3 → La0.7 − x Pb0.3 − x MnO3 + 0.5xLa2Sn2O7. Changes in the lattice parameter of the basic perovskite $R\bar 3c$ structure, the electrical resistivity, and the magnetic and magnetoresistance properties are caused by changes in the composition and content of a conducting perovskite ferromagnetic phase, the Mn3+/Mn4+ ratio, and the imperfection of vacancy and cluster types. An in-plane nanostructured cluster is formed by Mn2+ ions located in distorted A-positions. The detected anomalous magnetic hysteresis is induced by the appearance of a unidirectional exchange anisotropy at the boundary of an in-plane antifer-romagnetic cluster coherently joined with a ferromagnetic matrix structure. The broad asymmetric NMR spectra of 55Mn and 139La indicate a high-frequency Mn3+ ↔ Mn4+ superexchange and a nonuniform distribution of ions and defects. The constructed phase diagram characterizes a strong relation between the magnetic and transport properties in rare-earth manganites.

The magnetic and transport properties of anion- and cation-deficient Nd0.52Sr0.48MnO3 films with different thicknesses, as well as of two films from this system grown on different SrTiO3 and LaAlO3 substrates, are studied. Below Curie temperature T C, the films with different thicknesses exhibit phase separation: they represent magnetic clusters (drops) embedded in a nonconducting paramagnetic (at T > T N, where T N is the Neel temperature) or antiferromagnetic (T < T N) matrix. The temperature dependences of the resistivity of the films are well described in terms of the polaron mechanism of conduction. In external magnetic field H = 0.01 T, the drops may reach 15 nm in size. They consist of magnetic polarons with a small radius (1–2 nm). The drops are shown to interact with each other in the films. Because of competition between drop-drop dipole interaction and the magnetic energy, the drops disintegrate into droplets with a size comparable to that of a magnetic polaron in a field of 1 T. An explanation is given for the discrepancy between our results and the frequently observed growth of the drops with a rise in the external magnetic field. As the film gets thicker, the fraction of the ferromagnetic phase grows with thickness nonlinearly. In the film grown on SrTiO3 (compressed by 0.9%), the characteristic Neel and Curie temperatures are lower than in the film grown on LaAlO3. The diameters of ferromagnetic drops (both maximal at H = 0.01 T and minimal at H = 1 T) turn out to be roughly the same as in the films with different thicknesses.

The structure of (Nd0.7Sr0.3)1 − xMn1 + xO3 ± δ solid solutions with x = 0–0.2 (Nd: Sr atomic ratio maintained constant at 2.33) annealed at temperatures from 1200 to 1500°C has been studied by X-ray diffraction. The results demonstrate that, as the annealing temperature is raised, the atomic order in the stoichiometric (x = 0) materials is stable to changes in the homogeneity of the solid solution. In the case of the nonstoichiometric manganites with x = 0.15–0.20, an increase in annealing temperature is accompanied by the development of chemical and topological ordering processes in the matrix structure and cluster growth. The cluster size ranges from 100 to 250 A, and the largest percentage of clusters (3.5–5.5%) consist of the matrix phase. The fraction of clusters of binary composition, such as MnO-MnO2, is 0.5–2.0%.

The structure and properties of lanthanum strontium manganite perovskites La0.6Sr0.2Mn1.2 − y Cr y O3 ± δ (y = 0–0.3) sintered at 1430°C have been studied by X-ray, resistive, and magnetic (χac and 55Mn NMR) methods. The parameter of the rhombohedrally distorted (R $$ \bar 3 $$ c) perovskite structure decreases with increasing y. The real perovskite structure contains point (anion and cation vacancies) and cluster-type nanostructure defects. The analysis of asymmetrically broadened 55Mn NMR spectra has confirmed the high-frequency electron-hole exchange Mn3+ ↔ Mn4+ and local inhomogeneity of their surrounding by other ions and point and cluster-type defects. An increase in the Cr content leads to an increase in the resistivity and the magnetoresistive effect and a decrease in the metal-semiconductor and ferromagnetic-paramagnetic phase transition temperatures (T ms and T c ) due to the distortion of the exchange interactions Mn3+ ↔ Mn4+ by chromium ions, vacancies, and clusters. Introduction of Cr decreases the ferromagnetic component and increases the activation energy. The magnetoresistive effect near T ms and T c is caused by scattering of charge carriers from intercrystallite nanostructure inhomogeneities of the lattice, and the low-temperature effect is associated with the tunneling on mesostructural intercrystallite boundaries.

The effects of high pressure (3 GPa) and torsional strain on the structure and properties of compacts prepared from nonstoichometric lanthanum-strontium manganite La0.6Sr0.2Mn1.2O3 ± δ (LSMO) nanopowder with a perovskite structure have been studied for the first time using X-ray diffraction, low-temperature Ar adsorption, electron microscopy, and magnetic (χac, 55Mn NMR, and magnetoresistance) measurements. The laws governing the influence of this treatment on the structure, local valence and magnetic states of manganese ions and their inhomogeneous environment (involving other ions and defects), and on the resistivity, microstresses, coercivity, Curie temperature, and magnetoresistance of LSMO nanopowder compacts have been determined. A positive effect of several cycles of torsion under pressure on the magnetoresistance of this material has been observed for the first time.

Magnetoresistive ceramic samples La0.7Ca0.3 − x Sr x MnO3 ± δ sintered at temperatures of 1150 and 1350°C are investigated using X-ray diffraction, microscopic, resistance, and magnetic (χ, 55Mn NMR) measurements. The specific features of the influence of the composition on the type and parameters of the perovskite structure, its imperfection, the porous crystallite structure, the metal-semiconductor and ferromagnetic-paramagnetic phase transitions, the 55Mn NMR spectra, and the magnetoresistance effect are established. The magnetic phase diagram is constructed. The conclusions are drawn regarding the nonuniformity of the distribution of ions and vacancies around manganese involved in the high-frequency electron-hole exchange (Mn3+ ai Mn4+) and the nanostructured separation of the perovskite structure containing anion and cation vacancies, with the concentrations and magnetoresistance effect decreasing and the lattice parameters and phase transition temperatures increasing as calcium is replaced by strontium.

The main objective of the performed investigations was to enhance sensitivity of a current sensor to weak changes of magnetic field. New design of the sensor of current based on magnetoresistance effect – MRE (MRE = (RH - R0)/R0 , where RH is the resistance in magnetic field and R0 is the resistance without magnetic field) was developed. The sensor was produced in the form of an annular magnet with a gap, in which the (La0.7Sr0.3)0.8Мn1.2О3 manganite film possessing large negative MRE was inserted. Nominal current in a controllable electric circuit can change from a few tenths parts of ampere to a hundred of amperes. The limit detectable change of current value depends on the size of gap in the annular magnet. The operation time of sensor at current overload and short circuit is less than 0.3 sec. These magnetoresistors are thermally stable over the temperature range from (- 50 ° С) to (+ 50 ° С). Proposed sensors based on MRE can be applied in many electrical arrangements and devices.

The structure and properties of magnetoresistive ceramics La0.6Sr0.2Mn1.2 − x Co x O3 ± δ (x = 0−0.3) sintered at a temperature of 1200°C are investigated using x-ray diffraction, resistance, and magnetic (χ ac , M, 55Mn NMR) measurements. It is shown that the samples contain the rhombohedral (R $$ \bar 3 $$ c) perovskite (90%) and tetragonal (I41/amd) hausmannite (10%) phases. The lattice parameters of these phases decrease with an increase in the cobalt content x. The real perovskite structure involves point defects (anion and cation vacancies) and nanostructured defects of the cluster type. An analysis of the asymmetrically broadened 55Mn NMR spectra confirms the high-frequency electron-hole exchange between Mn3+ and Mn4+ ions and a local inhomogeneity of their environment by other ions and defects of the point and cluster types. An increase in the Co content leads to an increase in the electrical resistivity, an enhancement of the magnetoresistance (MR) effect, and a decrease in the magnetic susceptibility and the temperatures of the metal-semiconductor (T ms ) and ferromagnetic-paramagnetic (T C) phase transitions due to the suppression of the exchange interaction between Mn3+ and Mn4+ ions by vacancies and clusters. The introduction of cobalt results in a decrease in the ferromagnetic component and the activation energy. The magnetoresistance effect in the vicinity of the phase transition temperatures T ms and T C is associated with the scattering of charge carriers from intracrystallite inhomogeneities of the lattice, and the low-temperature magnetoresistance effect is governed by the tunneling at the intercrystalline boundaries.

Amorphous, nanocluster, and self-organizing bilayer Nd0.5Sr0.5MnO3 films are prepared by rf magnetron sputtering. The amorphous film turns out to be a typical paramagnet with free motion of the individual Mn spins, the magnetic properties of which are well described by the Curie-Weiss approximation. The nanocluster film manifests magnetic properties mimicking superparamagnetic particles with a nonclassical magnetic dynamics. The unique shape of the hysteresis loops, which have hysteretic lobes at high magnetic field but are nonhysteretic as the field crosses zero, suggests that each particle (nanocluster) is a closure magnetic domain (or magnetic vortex) rather than a single domian. At the same time, a blocked to unblocked transition was observed with increasing temperature, as in the usual superparamagnet. The self-organizing bilayer film demonstrates a negative exchange bias, which is typical for the ferromagnet/antiferromagnet hybrid system in spite of the fact that both layers in our case have a ferro...

The x-ray structural, resistive, magnetic, and Mn55 NMR methods are used to investigate the ceramic magnetoresistive lanthanum manganite perovskites La0.6Sr0.2Mn1,2−xFexO3 (x=0, 0.02, 0.05, and 0.1) annealed at 1170 and 1500°C. It is found that increasing the Fe content decreases the metal-semiconductor phase transition temperature Tms and the Curie temperature TC, and increases the peak of the magnetoresistive effect near these phase transitions and results in growth of the peak at low temperatures, where the magnetoresistive effect is due to tunneling transitions of carriers between crystallites. The wide asymmetric Mn55 NMR spectrum, whose resonance frequency shifts with increasing x to lower frequencies, confirms the high-frequency electron-hole exchange between the Mn3+ and Mn4+ ions and the high degree of lattice imperfections, including not only vacancies but also clusters. The hysteresis in the field dependences of the magnetization at 4.2K is due to a change in the fraction of low-spin Mn2+ in cl...

Ceramic samples of La31−xSr2+xMnO2−3 (x = 0, 0.1, 0.15, 0.2, 0.3, 0.4), sintered at different temperatures (1150, 1200, 1350, and 1500 °C) are investigated by means of methods of x-ray diffraction analysis and resistive and magnetic analysis. It is established that the perovskite structure parameter (a) and degree of its rhombohedric \((R\bar 3c)\) distortion (α) both decrease with increasing content of Sr2+ in La1−xSrxMnO3±δ (x = 0–0.4). The metal-semiconductor (Tms) and ferromagnetic-paramagnetic (Tc) phase transition temperatures and magnetoresistive peak temperature (Tp) all increase, while the activation energy (Ea) decreases. The density of defects in the lattice which contains anion (V(a)) and cation (in A and B positions) vacancies, average valency of manganese (ω), and tolerance factor (t) also increase. It is shown that with Sr2+ doping, charge compensation is achieved by two mechanisms, first, the Mn3+ → Mn4+ transition (∼80%), and second, the formation of V(a) vacancies (∼20%), with the contribution of the second mechanism increasing with increasing sintering temperature. With increasing x the magnetoresistive effect decreases at Tp and the lowfield tunneling magnetoresistive effect increases slightly. It is established that the concentration dependence of the intracrystaline peak magnetoresistive effect at Tp is opposite to the concentration dependence of the intercrystalline magnetoresistive effect in the semiconductor region for T ≪ Tp.

The effects of substitution of barium by tin on the phase composition, structural imperfection, and properties of lanthanum manganite perovskites La0.7Ba0.3−xSnxMnO3 (x=0, 0.1, 0.15, 0.2, 0.3) are established by comprehensive studies done by x-ray diffraction, resistive, and magnetic (including NMR on 55Mn and 139La) methods. It is shown that the introduction of Sn leads to the formation of a pyrochloric phase La2Sn2O7, to an increase in the density of lattice defects of the manganese-enriched main lanthanum manganite phase, and to a substantial decrease of the magnetoresistive effect. The smearing of the metal–semiconductor phase transition temperature is explained by an increase in the inhomogeneity and imperfection of the perovskite structure. The low activation energy is confirmed by a high degree of inhomogeneity and imperfection of the crystal lattice of the samples studied. The broad, asymmetric NMR spectra of 55Mn and 139La attest to high-frequency electron exchange between Mn3+ and Mn4+ and noneq...

The magnetic and transport properties of La1−xMn1+xO3 manganites with excess manganese are studied. It is shown that magnetic and charge ordering heavily depends on the superstoichiometric manganese content, magnetic field, and pressure. The magnetoresistive effect (MRE) is enhanced as the manganese concentration increases. In addition to the paramagnet-ferromagnet transition, the temperature dependences of the magnetization exhibit anomalies at low temperatures in samples with x=0.1–0.4. The magnetization decreases at T

A study is made of the external structure, magnetization, and magnetoresistive effect in ceramic samples of (La0.8Sr0.2)1−xMn1+xO3 annealed at 1150 and 1500 °C. It is shown that the additional annealing at 1500 °C leads to significant changes in the magnetization and increases the magnetoresistive effect by a factor of 2–3, depending on x. An “anomalous” magnetic hysteresis is observed on the initial parts of the magnetization curves in both ceramic and laser-deposited film samples. It is found that the value of the “anomalous” magnetic hysteresis depends on the composition of the samples (on x) and their annealing temperature. A mechanism for the appearance of the “anomalous” hysteresis is proposed, involving the presence and interaction of ferromagnetic and antiferromagnetic phases.

The Mossbauer and X-ray diffraction techniques are used to study the evolution of structure and chemical inhomogeneities in magnesium-zinc ferrites. These are the octahedral short-range environment of a magnetic Fe3+ ion, mesoscopic quasi-planar regions of size 100–200 A (clusters) with locally changed chemical composition and crystallographic order, and the general long-range order of the ferrite matrix. In each of these three inhomogeneities, the high-temperature long-term firing of the Mg-Zn ferrite (T=1280°C, τ=0–8 h) induces transitions (magnetic in the short-range order, concentration in the clusters, and structural in the matrix) within the time period τ=1–2 h. Subsequently, the structure stabilizes with the initial three-scale hierarchy retained.

The effect of Ba content on the phase composition, lattice parameter, Mn-55 NMR spectrum, resistance, and magnetoresistance of La0.6Sr0.4-xBaxMnO3 perovskites was studied. The lattice parameter of ...

The influence of the magnetic field strength (H=0, 2, 4, 6, 8 kOe), high hydrostatic pressures (P=0−1.8 GPa), and temperature (T=77−300 K) on the resistivity ρ, magnetoresistance (ΔR/R0), and phase transition temperatures in ceramic and thin-film samples of the lanthanum manganite La0.9Mn1.1O3±δ is investigated by x-ray-diffraction, magnetic, and resistive methods. It is found that with increasing H and P the resistivity decreases and the temperatures Tms of the metal-semiconductor phase transition and Tp of the magnetoresistance peak increase. The differences in the resistivities, magnetoresistances, and phase transition temperatures in the ceramics and laser-deposited films are explained by their different nonstoichiometry and defect density. The observed linear dependence of ρ and Tms on P suggests that lanthanum manganite ceramics and films could be used as pressure and temperature sensors.

The evolution of the hard and soft modes in the crystal structure of MnxZnyFezO4 manganese-zinc spinel ferrites is investigated theoretically and experimentally (x-ray structure analysis and magnetic measurements). It is shown that tetragonal and rhombohedral distortions of the cubic structure and fluctuations of the soft mode are accompanied by the formation of clusters in the form of quasi-two-dimensional fragments (50–200 and 400–1200 A), which involve families of γ-Mn2O3, γ-Mn3O4, and α-Fe2O3 oxide planes inherently bound to the spinel matrix.

The effects of magnetic fields H=0–8 kOe and high hydrostatic pressures P=0–2.2 GPa on the resistivity ρ, magnetoresistive effect ΔR/R0, metal–semiconductor phase transition temperature Tms, and peak temperature Tp of the magnetoresistive effect are investigated over a wide range of temperatures T=77–350 K in a ceramic target and a laser film of the same cationic compound La0.7Mn1.3O3±δ. Increasing H and P leads to a decrease of the resistivity. The observed difference in ρ, Tms, and Tp between the ceramics and film samples is explained by the difference of their oxygen nonstoichiometry. The magnetoresistive effect decreases with increasing H and decreases with increasing P. The temperatures Tms and Tp of the ceramics and film increase with increasing P, but the effect is stronger in the film. The observation of two phase transitions in the ceramics (the main transition at Tms=250 K and an additional transition at Tms′=210 K) is explained by its mesoscopic inhomogeneity of the cluster type.

The La 0.6 Sr 0.2 Mn 1.2− x Cr x O 3 (0⩽ x ⩽0.2) ceramic samples with perovskite-like structure (R 3 c) have been studied using the X-ray diffraction, NMR, magnetic and resistance methods. The 55 Mn NMR spectrum was shown to depend strongly on the Cr/Mn ratio. A single symmetric line centered at 379 MHz was found for La 0.6 Sr 0.2 Mn 1.2 O 3 ( x =0). For La 0.6 Sr 0.2 Mn 1.1 Cr 0.1 O 3 , the 55 Mn NMR spectrum is slightly expanded and shifted to lower frequencies. An analysis of the 55 Mn NMR spectrum for the La 0.6 Sr 0.2 MnCr 0.2 O 3 compound has shown that a wide asymmetrical line can be uniquely expanded into four components with different resonance frequencies. These components arise due to both different ionization states of the manganese ions and a non-equivalence of their crystallographic surrounding. There are manganese ions, whose ionization states are close to (3+) and (4+), as well as Mn ions with intermediate valence which resulted from the high-frequency electron exchange. The Curie temperature and the temperatures of both resistance maximum and magnetoresistance peak were found to decrease, while the value of magnetoresistance increases with increasing Cr content.

The spin-wave resonance (SWR) spectra have been observed in the (001) oriented La 0.7 Mn 1.3 O 3− δ epitaxial films. The spectra consist of a series of well-resolved spin-wave modes clearly seen in the perpendicular external field configuration. It is shown that the spins are completely pinned on both sides of the film surface. Based on a study of the SWR spectra the value of the spin-wave exchange constant, D , is found to be 150 meV A 2 . This value of D correlates well with this one determined for all known until now manganites.

Taking into account changes in the Cu charge states, general characteristics and distinctive features of structural transformations typical of high-temperature superconducting and ferroelectric phases in Y-Ba-Cu-Ti-O ceramic samples are studied. It is shown that with substitution of titanium for Y and Cu the concentration of Jahn-Teller ions Cu2+ detected by EPR technique does not rise higher than 10%. According to X-ray spectroscopy data, the Cu charge state lowers from Cu2.2+ to Cu0.5+ with increasing titanium content. It is found by X-ray diffraction studies that with increasing Ti content, the fraction of the layered structure containing (00l) planes of orthorhombic structure decreases and the growth of planes of the (11l) type pertaining to tetragonal structure is stimulated. The structural phase transition from the orthorhombic to tetragonal crystal structure mainly occurs in the range x=0.3–0.5.

Electrical resistivity and magnetoresistance (MR) measurements of La 0.7 Pb 0.3− x Sn x MnO 3 , 0 ≤ x ≤ 0.3, perovskite oxides have been performed for the first time. We have investigated the polycrystalline patterns and thin films as well. Typically the samples showed fairly large MR (10–15% at H = 1 T) in the temperature range 77–300 K. To find the PbSn-doping effect on the oxide magnetic phase and giant MR, 55 Mn and 139 La nuclear magnetic resonance measurements have been performed. We have found that one can obtain a large MR at room temperature in PbSn-doped LaMnO 3 thin films, avoiding the contamination of the perovskite phase.

Mesoscopic inhomogeneities and their influence on the behavior of the physical properties (optical reflectivity, dielectric constant, and Curie temperature) of a system of lead zirconate-titanate Pb0.85(Li1/2La1/2)0.15(Zr1−yTiy)O3 solid solutions are investigated. It is established that the disruptions of long-range order have a mesoscopic scale and generate ion groups in the form of interlayers of elements of binary-oxide planes coherently embedded in the crystal structure of the host phase. It is shown that the clustering of the structure is manifested in nonlinearity of the physical properties of the lead zirconate-titanate solid solutions, where the most pronounced variations are characteristic of the coexistence region of the antiferroelectric and ferroelectric phases.

Magnetoresistive properties of thin La0.5Pb0.2Ca0.2Y0.1MnO3−δ films obtained by magnetron sputtering technique are studied. A giant decrease in resistance (up to 98%) in magnetic fields H=10 T is observed at a temperature of 175 K. The physical factors responsible for the effect of composition and preparation technique on their magnetotransport properties are discussed. The mechanisms and empirical relations describing the temperature and field dependences of the resistive properties of films are also discussed.

Results of the study of mesoscopic inhomogeneities in the Pb 0.85 (Li1/2 La1/2) 0.15 (Zr1-y Tiy)03 solid solutions system are presented. It is demonstrated that these formations have some peculiarities in solid solutions for which FE and AFE phases coexist

Studies carried out using various methods — x-ray structural and spectral, electromagnetic, gravimetric, nuclear γ-resonance, and nuclear magnetic resonance — revealed that the crystal-chemical structure of mono-and polycrystalline manganese — zinc ferrites used in video tape recorders and color television sets possess defects, with various degrees of localization (point, plane, and cluster), existing simultaneously in both the cation and anion sublattices. Differences in the structure of mono- and polycrystalline specimens were observed, but the specimens were similar with respect to the nature of the clustered defects. A relationship between the defect structure and specified electromagnetic properties of the ferrites was established. It is concluded that more information is needed concerning the actual crystal-chemical structure of ferrites containing defects of different types and dimensions (micro, meso, macro).

We have observed an anomalous magnetic hysteresis in polycrystalline (ceramic) and single crystal (film) samples of La0.6Sr0.2Mn1.2O3−δ manganites with a perovskite structure. The anomaly is explained by the coexistence and interaction of two magnetic phases (ferromagnetic and antiferromagnetic) in these lanthanumcontaining manganites.

Atomic order and magnetoresistive parameters are studied in La0.6Sr0.2Mn1.2−yCryO3 ceramics, in which Cr substituted for the above stoichiometric Mn content serves to enhance cluster formation in a solid solution. It is shown that in a range of 0.05 0.1, of Cr2O3 type. It is shown that the structural phase transition is accompanied by maximum changes of the magnetoresistive parameters in the same range of Cr concentrations, i.e., 0.05