The magnetic-field dependences of the electrical resistivity Δρ/ρ0(Η) of the textured polycrystal Bi95.69Mn3.69Fe0.62 have been studied for the first time, for the H⊥I and H || I configurations at temperatures 5, 80, 150, and 300 K. It has been established that the Δρ/ρ0(Η) dependences significantly differ from those obtained for pure bismuth due to the influence of the internal magnetism of the α-BiMn phase inclusions on the behavior of charge carriers in the bismuth matrix. The maxima of Δρ/ρ0(Η) at H ≈ 30 and ≈ 40 kOe have been found, for the longitudinal and transverse magnetoresistance, respectively. These maxima may be related to reaching the quantum limit in the material we have studied.

Martensites of Ni-Mn-Ga-based alloys consist of hierarchical twinning domains spanning from micro- to nanoscale. This affects the diffraction pattern and thus can decrease the accuracy of the determination of the crystal structure. We propose a method to obtain different martensitic phases in Ni-Mn-Ga-Fe alloy with simplified variant microstructures and domain sizes of more than 2 micrometers. The use of simplified variant microstructures allows the influence of nanometer-scale domains on diffraction line position to be circumvented and enabls the comparison of the lattice parameters of non-modulated (NM), five-layered modulated (10M), and seven-layered (14M) phases in the same temperature range due to the large hysteresis of the intermartensitic transformations. It is found that the short crystallographic axes in NM, 14M, and 10M martensites at the same temperature have different lengths. As a result, equilibrium NM structure building blocks cannot be used to build the crystal structures of 14M and 10M martensites. Instead, we introduce a constant plane shift model with identical shift values of the nearest planes (110) along [1¯10] or [11¯0] as a replacement for the tetragonal building blocks model. The work demonstrates that plane shift values differ dramatically between martensites, which agrees with ab initio calculations. The application of the constant plane shift and hard sphere models in modulated lattices for atomic-level twinning considerations is discussed.

The ferromagnetic properties of Si:P in the region of a concentration insulator–metal phase transition at liquid helium temperatures have been detected and studied. To determine the spin component of the magnetization, the diamagnetic contribution linear in field has been subtracted from the total magnetizations of samples measured by a SQUID magnetometer. The spin magnetization has strong nonlinearity with saturation in fields of about several oersteds and a hysteresis loop, which are characteristic of ferromagnets. The capability of magnetization decreases sharply with the shift away from the phase transition point on the insulator side of the phase transition. However, it increases strongly at a nearly half degree of compensation of Si:P by acceptor impurities. The results indicate that the triplet state for some pairs of exchange-coupled spins (ferromagnetic phase) in Si:P in the region of the insulator–metal phase transition at low temperatures is more energy favorable than the singlet state (antiferromagnetic phase) largely because of a moderate compensation.

We study features of mobile carriers' skew scattering in nonmagnetic semiconductors emerging due to a combination of spin-orbit coupling in a crystal band structure and a nontrivial inner structure of impurities. In particular, we show that a nonzero magnetic moment of the impurity generally leads to the anomalous Hall effect (AHE) in the absence of the spin polarization of the mobile carriers, the effect arising from spin-independent scattering asymmetry due to exchange interaction. We analyze the skew scattering in bulk zinc-blende semiconductors for both electron and hole states and emphasize the crucial role of the impurity spin polarization for the emergent AHE for the valence band holes. We also revisit the skew scattering in quantum wells showing that the cancellation of the extrinsic contribution to the AHE common for two-dimensional systems can be lifted off depending on both the electron wave function and the impurity structure.

Magnetic anisotropy of needlelike single-crystal MnSb inclusions in an InSb matrix has been identified and investigated in the temperature range of 5–350 K. A power-law dependence of anisotropy constant K(T) on saturation magnetization MS(T) is observed in granular InSb–MnSb samples in the temperature range of 5–350 K with exponent n = 3.2 ± 0.4 in correspondence with the theories developed by Akulov, Zener, and the Callens.

We study the conductivity and magnetoresistance of the α‴ phase solid solution of (Cd1−xZnx)3As2 (x = 0.45). Single crystals of (Cd1−xZnx)3As2 are obtained by the modified Bridgman method. The space group and tetragonal lattice parameters of single crystals are found to be I41/amd and a = b = 8.56(5) Å, c = 24.16(6) Å. The temperature dependence of the conductivity and magnetoresistance is studied in the temperature range of 1.6–320 K and in the presence of a transverse magnetic field from 0 to 10 T. Mixed conductivity is analyzed using Hall resistivity data and standard quantitative mobility spectrum analysis. The concentration and mobility of holes are determined at different temperatures. The presence of two types of holes with different mobilities is demonstrated in the temperature range of 1.6–19 K, while with increasing temperature, just one type of charge carrier is observed in the mobility spectrum.

We theoretically analyze the dynamics of circular polarized photoluminescence (PL) associated with split-off states emerging in a semiconductor quantum well (QW) due to tunnel coupling with remote spin-split bound states. A mechanism for ultrafast PL polarization switching is proposed based on tunnel barrier transparency modulation. Such modulation can be experimentally realized by applying a gate voltage to the semiconductor heterostructure. The proposed mechanism is based on the split-off state energy level position being sensitive to the transparency of the tunnel barrier. The obtained results open the possibility to form fully polarized PL signal and are promising for applications in spintronics, in particular, for ultrafast polarization modulation in spin lasers.

Solid solutions of oxysulfides (RE0.95Ln0.05)2O2S (RE = La, Y; Ln = Ho, Tm) were obtained by hydrogen reduction of the co-precipitated sulfates followed by sulfidation of the reaction products. The crystal chemical characteristics of the obtained compounds were refined by the Rietveld method. Morphological certification of particles in the dynamics of synthesis was performed. Most of the particles produced by chemical reactions have a cut that indicates the formation of a compound with a hexagonal syngony with angles of 60 and 120°. This indicates that the thermal effect of gaseous reagents H2, H2S on sulfates leads to heterogeneous reactions of thermal dissociation and the formation of new phases. Steady state luminescence properties displayed characteristic sharp bands corresponding to 4f-4f transitions. Luminescence decay curves of all studied samples showed monoexponential decay with microsecond and hundreds microsecond lifetimes depending on doping ions. Calculated color coordinates of Ho3+ and Tm3+-doped powders make them promising candidates to be used as phosphors.

A number of solid solutions based on BaFe12-xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P6(3)/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V similar to 696.72 angstrom(3) was determined for the composition with x = 1.00 at T = 100 K, while the maximum value of V similar to 714.00 angstrom(3) is observed for the composition with x = 2.00 at T = 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The T-dif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from similar to 237.2 K to similar to 44.5 K, while the T-inf inflection temperature of the ZFC curve increases from similar to 21.0 K to similar to 23.8 K. With an increase in the doping concentration, both the D-av average and D-max maximum clusters grow up to similar to 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x > 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the T-C Curie temperature down to T similar to 600 K. The M-s spontaneous and M-r remanent magnetizations, as well as the B-c coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to M-s similar to 17.7 emu/g, M-r similar to 1.9 emu/g, and B-c similar to 3.9 x 10(-3) T, respectively. An interpretation of the magnetic state of the doped BaFe12-xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations. (C) 2020 Elsevier B.V. All rights reserved.

The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have been investigated. It is shown that these ceramics exhibit paramagnetic behavior in a wide temperature range from 10 to 300 K and their dielectric and magnetic properties are strongly influenced by the doping.

The magnetic and magnetotransport properties of thin Heusler alloy Ni 49.7 Fe 17.4 Co 4.2 Ga 28.7 films deposited onto MgO(100) substrates are studied over a wide temperature range, which includes a martensitic transition (MT). For this composition, the MT is not accompanied by a magnetic phase transition, since the martensitic and austenitic phases are ferromagnets with similar magnetizations. The electrical resistivity does not undergo sharp changes during the MT. The magnetoresistance is negative, decreases in magnitude with increasing temperature in the range 100–250 K corresponding to the MT, and then increases to –1%. The field dependences of the Hall effect resistivity have the shape that is characteristic of homogeneous ferromagnetic alloys. The coefficients of the normal and anomalous Hall effects are determined. The anomalous Hall effect coefficient is shown to be described by the relation R s = αρ + βρ 2 , where ρ is the electrical resistivity and the second term is lower than the first, which indicates an important role of the interference impurity–phonon scattering mechanism.

We report on Lu2(WO4)3: Yb3+, Tm3+ upconversion nanoparticles prepared via modified Pechini method, which is low-cost in comparison with analogs and allows achieving the homogenous rare earth ions (Yb3+ and Tm3+) dispersion in the host matrix. The Tm3+ doping concentration effect on structural and luminescence properties has been studied in detail. The structure of the nanoparticles was characterized by XRD and Raman spectroscopy. Both analytical methods confirmed the formation of single phase Lu2(WO4)3: Yb3+, Tm3+ nanoparticles without any impurities. It was found that thulium ions are uniformly incorporated into the tungstate structure up to a concentration of 1%. SEM images showed that prepared samples consisted of weakly agglomerated nanoparticles with an average size of about 40-80 nm. Emission and excitation spectra of all Lu2(WO4)3: xTm3+, 10% Yb3+ samples contained characteristic transitions inside Tm3+ ions. Upconversion spectra demonstrated intense infrared line (3H4-3H6) as well as weak blue 1G4-3H6 and two red (1G4-3F4, 3F2,3-3F6) bands obtained upon 974 nm excitation. Optimal Tm3+ doping concentration was found to be 0.3% for both 3H4-3H6 and 1G4-3F4 transitions. Change of chromaticity coordinates along with Tm3+ amount increase was also observed.

We present results of experimental studies of high-field magnetoresistance of Co–SiO 2 , Co–LiNbO 3 , CoNbTa–SiO 2 nanocomposites with metal volume fraction close to the percolation threshold. The nanocomposite films were deposited onto a glass-ceramic substrate by ion-beam sputtering at the growth temperature not exceeding 80°C. Magnetization was measured using a superconducting quantum interference device (SQUID) magnetometer in the temperature range of 4.2–300 K. Out-of-plane magnetoresistance was measured in a pulsed magnetic field up to 20 T in the temperature range of 4.2–300 K with the pulse duration of 11–12 ms. In addition to negative magnetoresistance, a linear positive contribution to magnetoresistance was observed in high magnetic fields for nanocomposites with the composition close to the percolation threshold. This effect was explained by the influence of the Zeeman effect on the tunnel barrier height. It is shown that the unconventional anisotropy of magnetoresistance of Co–LiNbO 3 is associated with the peculiarities of its microstructure.

A layer-by-layer sputtering method was used to fabricate nanostructures (ZnO/C)(25) composed of zinc oxide and carbon alternating layers, with a total multilayer thickness of 146 nm and 153 nm. At low temperatures, the multilayers show signatures of local ferromagnetic order: magnetic hysteresis, weak magnetization and the characteristic shape of the thermomagnetic curve. In-plane and out-of-plane magnetoresistance (MR) was measured in a pulsed magnetic field up to 20 T in the temperature range of 15-300 K. At T <= 20 K, MR changed its sign from negative in low magnetic fields to positive in moderate fields, and then back to negative in high magnetic fields. At T >= 80 K, MR was negative in the full range of magnetic fields studied. The unusual MR behavior can be associated with the influence of the Zeeman effect on the Fermi level position in the case of 2D variable hopping conduction along the interfaces, scattering on magnetic heterogeneities and the effect of magnetic blockade.

Abstract A number of solid solutions based on BaFe12-xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P63/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V ~ 696.72 A3 was determined for the composition with x = 1.00 at T= 100 K, while the maximum value of V ~ 714.00 A3 is observed for the composition with x = 2.00 at T= 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The Tdif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from ~ 237.2 K to ~ 44.5 K, while the Tinf inflection temperature of the ZFC curve increases from ~ 21.0 K to ~ 23.8 K. With an increase in the doping concentration, both the Dav average and Dmax maximum clusters grow up to ~ 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x \u003e 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the TC Curie temperature down to T ~ 600 K. The Ms spontaneous and Mr remanent magnetizations, as well as the Bc coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to Ms ~ 17.7 emu/g, Mr ~ 1.9 emu/g, and Bc ~ 3.9*10-3 T, respectively. An interpretation of the magnetic state of the doped BaFe12-xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations.

The magnetic anisotropy of needle-like single-crystal MnSb inclusions in the InSb matrix was determined and studied in the temperature range 5 – 350 K. In granular InSb-MnSb samples a power-law dependence of the anisotropy constant K(T) on the saturation magnetization MS(T) is observed in the temperature range 5 – 350 K with an exponent n = 3.2 ± 0.4 in accordance with the theories developed by Akulov, Zener, and Callens.

The stability of the nonmodulated martensitic phase, the austenitic Fermi surface, and the phonon dispersion relations for ferromagnetic ${\mathrm{Ni}}_{2}\mathrm{MnGa}$ are studied using density functional theory. Exchange-correlation effects are considered with various degrees of precision, starting from the simplest local spin density approximation (LSDA), then adding corrections within the generalized gradient approximation (GGA), and finally, including the meta-GGA corrections within the strongly constrained and appropriately normed (SCAN) functional. We discuss a simple procedure to reduce a possible overestimation of magnetization and underestimation of nesting vector in SCAN by parametrically decreasing self-interaction corrections.

Recently, much attention has been paid to the development of new microminiature solid-state cooling devices and heat energy converters based on the electrocaloric effect. But researchers pay little attention to aspects of the electrocaloric effect associated with its time and frequency characteristics. These phenomena must be taken into account when developing highly efficient thermodynamic cycles for solid-state cooling devices. In this work, we conducted an experimental study of the dependence of the electrocaloric response of a ferroelectric sample on the period and duty cycle of the control signal was studied. It was demonstrated, that value of electrocaloric response in studied ceramics may vary by more then 15% depending on period and duty cycle of electric pulses.

Introduction. Resonators based on epitaxially grown single-crystal films of yttrium iron garnet are used in various applications of microwave electronics. It is known that with increasing of microwave power incident on a resonator, various nonlinear effects begin to manifest themselves. There are: bistability effect, nonlinear frequency shift, nonlinear damping, etc. By now, the listed nonlinear effects have been quite good studied experimentally. Previously, when describing oscillations of various dynamical systems, the nonlinear damping and the nonlinear frequency shift were usually considered separately. At the same time, it was known that, when studying nonlinear magnetization oscillations in ferromagnetic film resonators with an increase in oscillation amplitude, these effects could occur simultaneously.Aim. Development of a model of magnetization oscillations taking into account the nonlinear frequency shift and nonlinear damping, as well as its experimental justification for a ferromagnetic film resonator.Materials and methods. The development of the model was carried out by the method of slowly varying amplitudes. An experimental study was carried out with a ferromagnetic film resonator. For the measurements, we used Rohde & Schwarz ZVA 40 vector network analyzer. We measured the frequency dependence of the reflection coefficient of the microwave signal from the resonator.Results. A model of nonlinear magnetization oscillations was developed taking into account both a nonlinear frequency shift and a nonlinear attenuation. The resonance curves were experimentally measured at various levels of the microwave power incident on the resonator. It was shown that nonlinear damping limits the nonlinear frequency shift of the magnetization oscillations in a tangentially magnetized ferromagnetic film resonator.Conclusion. The developed model adequately describes behavior of the resonance curves of ferromagnetic film resonators at high microwave power levels. The nonlinear damping leads to broadening of the resonance curves, thereby increasing losses. This effect also increases the reflection coefficient of the microwave signal from the resonator.

Accurate thermal sensing with good spatial resolution is currently required in a variety of scientific and technological areas. Luminescence nanothermometry has shown competitive superiority in contactless temperature sensing, especially at the nanoscale. To broaden the use of such thermometers, development of a novel sensor type with high sensitivity and resolution is highly demanded. Herein, we report single-phase Ln3+-doped YVO4 nanophosphors synthesized using a modified Pechini method as multimode optical thermometers for wide-range temperature probing (299-466 K). The observed temperature-induced red shift of the charge transfer band was utilized to provide thermal sensing. Temperature sensing was based on the luminescence intensity ratio using emission intensities obtained upon charge transfer and direct lanthanide excitation, the spectral position of the charge transfer band and its bandwidth. The suggested probing strategies provided a high relative thermal sensitivity (up to 3.09% K-1) and a precise temperature resolution (up to 0.1 K). The obtained results can be useful for the design of novel contactless luminescence thermometers.