Spacecraft electronics and onboard computer microchips are made of semiconductors. Radiation increases in near-Earth orbit, especially during solar flares, where the flux of high-energy particles and gamma radiation increases. This leads to defects in semiconductor transistors and failure of electronic devices. Therefore, replacing field-effect transistors with spintronics, which utilizes the spin degree of freedom of electrons, is becoming a pressing issue. Transport characteristics can be controlled by a magnetic field using samarium-substituted manganese sulfides. The conductivity of a sample was studied at low current in a magnetic field applied at an angle to the current, varying from 0° to 360°. Without a magnetic field, the conductivity remains constant. When a magnetic field is applied and the sample rotates, a change in conductivity is observed. In a magnetic field, conductivity decreases and reaches a minimum within a certain angular range. Upon heating, conductivity decreases in a magnetic field and reaches one order of magnitude near the magnetic phase transition. The current-voltage characteristics of SmxMn1–xS with a concentration of x = 0.1 were measured without a magnetic field of H = 0 kOe and in a magnetic field of H = 12 kOe, directed along the current and perpendicular to the current. The dependence of current on voltage is nonlinear and is associated with electrically inhomogeneous states in the sample. From the current-voltage characteristics, the dependence of the change in conductivity in a magnetic field on the current (voltage) and temperature was found. The maximum decrease in conductivity in a magnetic field was found at 200 K. Above room temperature, conductivity decreases by several percent due to the Hall contribution. Heating and increasing current lead to a decrease in magnetoconductivity. A comparison of the two methods for measuring conductivity in a magnetic field indicates that the regulation of conductivity by a magnetic field depends on the current value at which the conductivity is measured.

The effect of nonstoichiometry in manganese selenide (MnSe)1-& khcy;(Tm0.76Se)& khcy; (0 <= x <= 0.3) substituted with thulium of variable valence on the magnetic, structural, and magnetoelastic properties of the compound has been studied. The magnetic susceptibility in the temperature range of 80-1000 K, infrared spectra (IR) in the frequency range of 400-7500 cm-1 at temperatures of 80-500 K, thermal expansion coefficient, electrostriction, and magnetostriction of the compound have been experimentally determined. The maximum paramagnetic susceptibility, thermal expansion coefficient, and IR absorption frequency shift and the critical temperatures and frequencies at which the IR absorption vanishes have been found above the Neel temperature. A model of bipolarons with vacancies in the anion subsystem has been proposed. Anomalies in the magnetic and structural characteristics of the investigated compound have been explained by the bipolaron dissociation accompanied by a singlet-triplet transition and vacancy recombination. The temperatures of the onset of the piezoelectric effect and magnetostriction induced by the loss of inversion in clusters with thulium and the formation of ferromagnetic exchange between thulium and manganese ions have been established. It is shown that the negative thermal expansion coefficient is caused by the competition of the ferro- and antiferromagnetic interactions.

The effect of cation nonstoichiometry and variable-valence samarium ions on the thermoelectric and structural characteristics of manganese sulfide is studed. Nonstoichiometry leads to a change in the thermopower sign in the antiferromagnetic region in a magnetic field and a decrease in the thermopower in the paramagnetic region. It is shown that the thermopower and Nernst–Ettingshausen coefficient of samarium-substituted manganese sulfide change their signs in the vicinity of structural and electronic transitions established from the thermal expansion coefficient. A decrease in the sound attenuation in a magnetic field is found. A correlation between the temperatures of the change of the sign of the Nernst–Ettingshausen effect and the change in electrosound in a magnetic field is established and explained within the model of carrier diffusion in the phase transition region. The conductivity control by the ultrasound is demonstrated.

Control of transport characteristics under the influence of a magnetic field is promising from the point of view of creating magnetic field sensors resistant to radiation. The impedance and its components in thulium manganese chalcogenide in the frequency range of 102–106 Hz are studied. The temperature range with a prevailing contribution of the reactive and active parts of the impedance is found. The impedance components are described in the Debye model. When manganese is replaced by thulium ions, the frequencies of the maxima of the imaginary component of the impedance shift toward high frequencies in manganese selenide by two orders of magnitude. With an increase in the concentration of substitution by thulium ions in selenides, two relaxation times are found, compared with sulfides. The activation nature of the relaxation time, the activation energy from the concentration of thulium ions are found. An increase in impedance in a magnetic field in the region of low concentrations and a change in the sign of the impedance with temperature for high concentrations are established. Magnetoimpedance in chalcogenides passes through a maximum when heating the samples. The increase in impedance in a magnetic field is due to a change in the diagonal component of the permittivity in a magnetic field, which is proportional to the conductivity. A positive value of magnetoimpedance is described in the model of an electrically inhomogeneous medium. From the impedance, information can be obtained about the electrical inhomogeneity of the material.

The effect of the size of Bi2Fe4O9 and BiFeO3 nanoparticles on the magnetoelectric interaction in the Bi2Fe4O9/BiFeO3 composite with a percentage ratio of 67/33 has been studied. The electrostriction and electric polarization on electric and magnetic field in wide temperature range has been measured. The hysteresis of the polarization and I‒V characteristics has been found. Temperature ranges with activation and hopping types of conductivity have been found. The mechanism of electric polarization and the crossover temperature from dipole polarization to migration polarization at 260 K have been established. Linear and quadratic contributions to the magnetoelectric effect have been found. Below 120 K the linear contribution is an order of magnitude greater than the quadratic contribution and above 240 K the quadratic contribution to the ME effect prevails. Models have been proposed to explain the enhancement of the magnetoelectric effect as a result of the migration polarization in mullite and linear magnetoelectric effect in bismuth ferrite. The correlation of temperatures of the extremum of the temperature coefficient of the electrical resistance and the magnetic phase transition in mullite at 260 K indicates a polaron-type conductivity and a strong electron‒phonon interaction. A change in the sign of the electrostriction coefficient upon heating and the compression temperature of the composite in an electric field was found.

The MnXTm1-XSe (0 <= & KHcy; <= 0.2) solid solutions have been first synthesized and their structural, magnetic, and transport properties have been studied in the temperature range of 80-1000 K and magnetic fields of up to 12 kOe. The surface morphology of the samples has been examined and the chemical analysis has been carried out. It is shown that the valence change with the increasing substitution concentration is accompanied by a change in the lattice parameter and a decrease in the magnetic moment of the samples. The Kondo temperatures caused by the manganese and thulium subsystem have been found in the low- and room-temperature regions. The temperature of localization of small-radius polarons has been determined. A drastic decrease in the relaxation time in the range of the manganese ion percolation through the lattice in the MnXTm1-XSe system has been established. The change of the current carrier type upon variation in the temperature and substitution concentration was determined from the Seebeck coefficient. A high-temperature extremum of thermopower was revealed, which is explained within the framework of the Anderson model.

The magnetic, transport and acoustic properties of materials TmXMn1−XSe (0.025 ≤ X ≤ 0.2) have been studied in magnetic fields of up to 12 kOe at temperatures of 80‒600 K. The magnetic phase transition temperatures (TN) and change in the sign of resistance at DC current in vicinity of the TN were established. The temperature and concentration ranges corresponding to the maximum magnetoresistance (− 50

Manganese chalcogenides, which are promising for the manufacture of thermoelements, are being studied. The current is measured in the temperature range of 80–500 K, in the absence of external voltage, which can be caused by a temperature gradient (thermopower), a change in electrical polarization (pyroelectric current), piezoelectric current (when the sample is deformed, a potential difference arises) or thermionic emission (thermal emission current) . Temperatures of current anomalies and their relationship with thermionic current and polarization current are found. A change in electrical polarization withtemperature will cause a pyroelectric current. Compensation for excess electrical charge will result in local electrical polarization. Partial decompensation will cause the formation of an electric field in the sample. The critical temperatures for the disappearance of electric polarization were determined for different concentrations. In the region of concentration of thulium ions flowing through the lattice, the activation nature of the thermionic current was established and the activation energy was found. The pyroelectric current has a smaller value compared to the thermionic current. The current mechanism is determined by the emission of electrons from deep traps and the temperatures of the maximum thermionic current correlate with the temperatures at which IR absorption disappears. The electric current density and its value depend on the type of substituted rare earth element are calculated.

Polycrystalline samples Mn1–xGdxS and Mn1–xYbxS with a concentration x = 0.2, near the concentration of ion flow through the fcc lattice, are studied in order to determine fluctuations in the valence of the ytterbium ion on dielectric properties. Dielectric constant and dielectric losses were determined from measurements of capacitance and loss tangent in the frequency range 102–106 Hz at temperatures of 80–500 K without a magnetic field and in a magnetic field. The magnetic capacity and dielectric losses in the magnetic field of the sample were determined from the relative change in the real and imaginary parts of the dielectric constant of the sample in a magnetic field H = 12 kOe applied parallel to the capacitor plates. A temperature range with a sharp increase in dielectric constant and with a maximum dielectric loss has been discovered, which shifts with increasing frequency and magnetic field. An increase in dielectric constant and dielectric losses in a magnetic field above 170 K was found in Mn1-xYbxS. The increase in dielectric losses is explained by an increase in relaxation time, as a result of local deformations near ytterbium ions during valence fluctuations. The mechanism for reducing reactance in a magnetic field in Mn1–xYbxS at low frequencies due to capacitance, and at high frequencies due to inductance, has been determined. In the Mn0.8Gd0.2S compound, the imaginary part of the dielectric constant has two maxima. The low-temperature maximum shifts in a magnetic field towards high temperatures and is described in the model of localized electrons with freezing of dipole moments. Dielectric losses decrease in a magnetic field. The magnetic capacity decreases by an order of magnitude in Mn0.8Gd0.2S compared to Mn0.8Yb0.2S. The dielectric constant in both compounds is described in the Debye model with the activation dependence of the relaxation time on temperature, where the activation energies differ for ytterbium and gadolinium ions.

The composite compound Bi2(Sn0.7Fe0.3)2O7/Bi2Fe4O9 in the ratio 91/9% was synthesized by the solid-phase reaction method. The current-voltage characteristics were studied in the temperature range 800-400 K. The hysteresis of the current-voltage characteristics was found. The magnetoelectric interaction and thermoelectric power have been studied. The temperatures of predominance of the even and linear functions of the magnetoelectric effect are established. The sign change of the thermopower has been found.

The components of the impedance, the impedance of the LuxMn1-xS (x<0.2) solid solution in the temperature range of 80-500 K and the frequency of 100-106 Hz were studied. A change in the sign of the magnetoimpedance in concentration and temperature is found. The contribution of the reactive and active components to the magnetoimpedance is determined. The correlation of magnetoimpedance temperatures with the temperatures of the maximum attenuation of ultrasound and electrosound has been established. The frequency dependences of the reactive part of the impedance are described in the Cole-Cole model. Keywords: Semiconductors, impedance, magnetoimpedance, attenuation of ultrasound.

The magnetic properties and Mo & BULL;ssbauer spectra of the Y1.8Bi1.2Fe3.5Ga1.5O12 compound were investigated. A linear temperature dependence of the saturation magnetization, hysteresis, and stability of the coercive field in the magnetically ordered state were found. Using the Mo & BULL;ssbauer measurements, the distribution of iron ions over octahedral and tetrahedral sites and the concentration of paramagnetic iron ions were determined. Two critical temperatures - the sublattice magnetization compensation temperature and the ferrimagnet-paramagnet transition temperature - were established. The disappear of the phonon mode in the vicinity of the magnetic transition was observed. The experimental data have been interpreted in terms of the spin-lattice interaction model.

Sequence of structural transitions in the magnetically ordered region and a displacement-type structural tran-sition at T = 220 K accompanied by the variation in the thermal expansion coefficient, ultrasound attenuation coefficient, g factor, and polarization current in the polycrystalline compound Ho0.1Mn0.9S was found. The electronic transitions above room temperature were established on the basis of the measurements of the con-ductivity, ultrasound attenuation maxima, and IR spectra.

The role of defects on the dynamic characteristics of manganese sulfide is studied by impedance spectroscopy in the frequency range 102–106 Hz and temperatures 80–500 K. Nonstoichiometry plays an important role in the formation of new transport and magnetic properties, as it leads to electrically inhomogeneous states. The phase composition and crystal structure of nonstoichiometric manganese sulfide were studied on a DRON-3 X-ray unit using CuKα – radiation at room temperature. According to X-ray diffraction analysis, the synthesized compound is single-phase and has a NaCl-type cubic lattice. From the frequency dependences of the impedance components measured in the absence of a field and in a magnetic field, the relaxation time of the current carriers in the Debye model is found. A sharp decrease in the relaxation time and its correlation with conductivity were found. The contribution to the impedance of the active and reactive parts of the impedance at frequencies below and above the relaxation time is established. The capacitance from the impedance hodograph in the equivalent circuit model is determined. In defective manganese sulfide, the temperature-dependent impedance has an activation character. The activation energy is determined in the range 250–500 K, which is attributed to the excitation energy of lattice polarons. The effect of a magnetic field on the dynamic characteristics of current carriers was studied as a result of a change in the impedance components in a magnetic field at fixed temperatures. The impedance increases in a magnetic field and reaches a maximum in the temperature range of charge ordering of vacancies. An increase in the impedance in a magnetic field is explained by a decrease in the diagonal component of the permittivity in a magnetic field in an electrically inhomogeneous medium. The experimental data are explained in the Debye model.

In contrast to BiFeO3, samples of BiFe1 − xMnxO3 solid solution (x = 0.05 and 0.15) are ferromagnets and semiconductors. Raising x lowers the Curie temperature (TC = 605 K when x = 0.05 and 550 K when x = 0.15) and increases dielectric permittivity ε at room temperature. The drop in the value of specific magnetization as x rises is due to redistribution of the volumes of ferromagnetic and antiferromagnetic phases.

Magnetic semiconductors are widely used in microelectronics, which is used to control spacecraft. The transport and electrical properties depend on the magnetic structure, which can be changed by the action of the magnetic field and controlled by the current. The magnetic structure of semiconductors with a strong spin-lattice interaction, which is reduced to a four-spin exchange interaction, is investigated. The magnetic characteristics are calculated in a classical Heisenberg model constructed from equivalent magnetic atoms forming a simple cubic and square lattice. The Hamiltonian of the system contains the exchange interaction between the nearest neighbors, the four-spin exchange, and the one-ion anisotropy of the light axis type. The Monte Carlo method calculates the thermodynamic characteristics: the sublattice magnetization, the quadrupole parameter, the pairwise spin-spin correlation functions, the spontaneous moment at the node directed along the light axis and in the basis plane, the internal energy, and the magnetic susceptibility. The magnetic order type was found to change from a collinear antiferromagnet (AFM) to a noncollinear (NAF) as the four-spin exchange constant increases. The dependence of the spin correlation functions on the distance has a weakly damped oscillatory character. In the AFM-NAP transition region, the near antiferromagnetic order is replaced by the ferromagnetic one, while the far antiferromagnetic order is preserved. A phase diagram of the antiferromagnetic (AFM) and non-collinear (NAF) on square and cubic lattices is constructed on the four-spin exchange-single-axis anisotropy plane. The longitudinal and transverse susceptibility of the NAF from temperature for different parameters of the four-spin exchange is calculated. The region of anisotropy and quadrupole exchange parameters in noncollinear NAF with a first-order phase transition, the sublattice magnetization jump, and the quadrupole parameter from temperature are determined. The anisotropy and four-spin exchange constants in a classical antiferromagnet with spontaneous momentum and far- and near-order parameters were found.

The samples of BiFe1 – xMnxO3 solid solution system (x = 0.05 and 0.15) are ferromagnetics and semiconductors unlike BiFeO3. Growth of x leads to a decrease in Curie temperature (TC = 605 K for x = 0.05 and 550 K for x = 0.15) and growth of dielectric permittivity ε at room temperature. The decrease in the value of specific magnetization with increasing x is due to the redistribution of the volumes of ferromagnetic and antiferromagnetic phases.

The components of the impedance, the impedance of the LuxMn1-xS solid solution (x < 0.2) in the temperature range of 80-500 K and the frequency of 100-106 Hz were studied. A change in the sign of the magnetoimpedance in concentration and temperature is found. The contribution of the reactive and active components to the magnetoimpedance is determined. The correlation of magnetoimpedance temperatures with the temperatures of the maximum attenuation of ultrasound and electrosound has been established. The frequency dependences of the reactive part of the impedance are described in the Cole-Cole model.

A Bi2Fe4O9/BiFeO3 composite with a percentage ratio of 67/33 has been synthesized, its morphological analysis has been carried out. The average crystallite sizes for each phase have been determined. The magnetization hysteresis has been established and the temperature of its disappearance has been found. Using the infrared absorption spectra, temperatures of the magnetic phase transitions in each phase have been determined from the magnetic susceptibility, magnetostriction constant, ultrasound damping coefficient, and phonon mode softening. The change of magnetostriction constant sign observed in the vicinity of the spin reorientation transition and antiferromagnetic transition in mullite has been attributed to the change of the sign of the magnetoelastic constants. The interaction between the phases in the composite and the correlation of its structural and magnetic properties have been established.