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Based on the results of the Shubnikov-de Haas oscillations study in single-crystalline diluted magnetic semiconductors (Cd1−x−yZnxMny)3As2 (CZMA) with х + y = 0.2 and Mn content (у = 0.02, 0.04, 0.06, 0.08) at temperatures T = 4.2 to 30 K and magnetic fields B = 0 to 12 T under hydrostatic pressure p = 0 and 10 kbar, the values of the phase shift β, indicating the existence of the Berry phase in all samples were determined. Thickness of two-dimensional surface topological nanolayers in CZMA (х + y = 0.2) single crystals was defined. The rise in Mn concentration led to an increase in the concentration of charge carriers in the 2D surface layers n 2D and a decrease in its mobility μ 2D. The reduced cyclotron mass m с (0)/m 0, depending on the Fermi wave vector k F , experimentally observed from the Shubnikov-de Haas oscillations, which was in a good agreement with the prediction theory of linear dependence and experimental results in topological insulator single crystals Bi2Se3 indicated that Dirac fermions were present in a diluted magnetic semiconductor CZMA system with х + y = 0.2. The damping of the Shubnikov-de Haas oscillations for pressures p = 0 and 10 kbar in the CZMA sample (х + y = 0.2; y = 0.2) was found to be associated with an amplitude decrease by spin splitting (Zeeman effect). From the analysis of experimental data, the effective Lande factor g = 7.63 and 7.87 and the band gap Δ =35.3 and 9.7 meV at p = 0 and 10 kbar, respectively, were obtained.

Young's modulus of tapered mixed composition (zinc-blende with a high density of twins and wurtzite with a high density of stacking faults) gallium phosphide (GaP) nanowires (NWs) was investigated by atomic force microscopy. Experimental measurements were performed by obtaining bending profiles of as-grown inclined GaP NWs deformed by applying a constant force to a series of NW surface locations at various distances from the NW/substrate interface. Numerical modeling of experimental data on bending profiles was done by applying Euler-Bernoulli beam theory. Measurements of the nano-local stiffness at different distances from the NW/substrate interface revealed NWs with a non-ideal mechanical fixation at the NW/substrate interface. Analysis of the NWs with ideally fixed base resulted in experimentally measured Young's modulus of 155 +/- 20 GPa for ZB NWs, and 157 +/- 20 GPa for WZ NWs, respectively, which are in consistence with a theoretically predicted bulk value of 167 GPa. Thus, impacts of the crystal structure (WZ/ZB) and crystal defects on Young's modulus of GaP NWs were found to be negligible.

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.

Fe73.9Cu1Nb3Si13.2B8.9 thin films were deposited on the glass substrates by means of ion-plasma radio frequency sputtering. Heat treatment at temperatures of 350, 400 and 450 °C was performed for 30 minutes in order to control thin film structural state. The X-ray powder diffraction showed that the crystallization of α-Fe(Si) nanograins took place at the temperature of 420 °C whilst the other samples stayed in the amorphous state. The magnetic microstructure of the Fe73.9Cu1Nb3Si13.2B8.9 films was discussed in the framework of random anisotropy model and law of approach of magnetization to saturation. The parameters of magnetic microstructure were determined, and relations between structure and macroscopic magnetic properties were interpreted by means of magnetic microstructure analysis.

Barium titanate based ceramics is the most common class of lead-free ceramics due to its high values of dielectric constant, polarization, piezo- and electrocaloric effects. In this paper dielectric properties and electrocaloric effect in ceramics based on solid solution of barium-calcium titanate had been studied. It was shown, that increasing of calcium titanate in solid solution leads to increasing of dielectric constant and electrocaloric effect, simultaneouslyit leads to decreasing of leakage currents. While increasing fraction of calcium titanate from 0% to 10%, dielectric constant at frequency of 1 kHz rises from 10500 to 13600, maximum adiabatic electrocaloric response at ΔE = 1.3 V/μm rises from 0.5 K to 0.7 K.

In this work, we investigate variations of surface potentials along a single gallium phosphide (GaP) nanowire (NW) synthesized with a mixed crystal phase along the growth direction. GaP NWs synthesized with both wurtzite (WZ) and zincblende (ZB) phases were studied. The measurements were performed on a standard Atomic Force Microscopy (AFM) set-up equipped with Kelvin Probe Force Microscopy (KPFM) module in PeakForce Tapping Mode. KPFM Measurements from two structures were analyzed. Variations of surface poten-tials were observed in a single GaP NW with WZ/ZB segments. An average difference in surface potential was 55±11 mV. This is explained by different crystal structures along the NW. The work expands the understanding of crystal structure-dependent electrical transport properties of GaP NWs.

Achieving a combination of real-time diagnosis and therapy in a single platform with sensitive thermometry and efficient heat production is a crucial step towards controllable photothermal therapy. Here, Nd3+-doped Y2O3 nanoparticles prepared using the combined Pechini-foaming technique operating in the first and second biological windows were demonstrated as thermal sensors within the wide temperature range of 123-873 K, and as heaters with a temperature increase of 100 K. Thermal sensing was performed based on various approaches: luminescence intensity ratio (electronic levels; Stark sublevels), spectral line position and line bandwidth were used as temperature-dependent parameters. The applicability of these sensing parameters, along with relative thermal sensitivity and temperature resolution, are discussed and compared. The influence of Nd3+-doping concentration on thermometer and heater efficiency was also investigated.

The method of measuring nanowires elastic modulus by scanning probe microscopy is presented. This method uses the measurement of nanowire bending profiles in the precise force control mode. The possibilities of the method are demonstrated by measuring the Young's modulus of thin tapered InP nanowires.

The temperature dependence of the resistivity, ρ, of ceramic LaMnO3+δ with δ = 0.065 and 0.154 (or simply # 065 and # 154), is investigated under hydrostatic pressure, p, between the temperatures T = 80 and 320 K in magnetic fields up to 10 T. The data for ρ(T) are analysed within a Shklovskii–Efros-like variable-range hopping conductivity model, governed by a soft Coulomb gap, Δ, and a rigid gap, γ, in the density of localized states. The validity of this approach to the resistivity of LaMnO3+δ under ambient pressure was established in recent investigations (Laiho et al 2005 J. Phys: Condens. Matter 17, 105). In the present work it is shown that upon increasing p up to 11 kbar (# 154) and 13 kbar (# 065) the magnetic Curie temperature, TC, is increased by ~12–13%. Correspondingly, Δ(p) is decreased by ~7–8% and γ(p) by ~8% in # 154 and 12% in # 065. Similarly, the electron localization radius a(p) is increased by ~4% in # 154 and 8% in # 065, respectively. The influence of pressure on TC, Δ, γ and a is interpreted by increasing the electron bandwidth and decreasing the polaron potential well, which stimulates the delocalization of electrons when p is increased.

The Hall effect in the II–V group semiconductor n-CdSb doped with In is investigated in pulsed magnetic fields up to B = 25 T and temperatures between T = 2 and 77 K for samples oriented along the [0 1 0] and [0 0 1] crystallographic axes. The Hall coefficient, R (B, T), exhibits a sequence of an almost flat region followed by a descending interval and an upturn when B is increased. The decrease of R (B, T) is interpreted by the presence of two groups of electrons with concentrations n2(T) > n1(T) and mobilities μ2(T) < μ1(T). Analysis of n1(T) and n2(T) demonstrates that the high-mobility carriers n1 are the conduction band (CB) electrons, whereas the low-mobility carriers n2 are itinerant electrons of a lower resonant impurity band (IB), having at low T energies of Ei ~ 3–4 meV above the CB edge. In addition, near the CB edge lies a higher IB containing only localized electron states. The IBs are split by spin to states differing by an energy ΔEi ≈ 0.9 meV. The upturn of R (B, T) in the high-field region is explained by the redistribution of the electrons between the IBs due to the decrease of ΔEi when B is increased. The mobility of the CB electrons is determined presumably by strong anisotropic scattering on neutral impurity centres, accompanied at high T by isotropic scattering on acoustic phonons, whereas scattering from ionized impurities is small.

The Hall coefficient, electrical conductivity and electron mobility are investigated in Ag-doped n-ZnSe single crystals at temperatures between 8 and 500 K immediately after doping the samples and after storing them for 5 years under normal room conditions in darkness. The formation of donor-type Agi interstitial defects stimulated by time is found for the first time. After 5 years storage, the samples show a dramatic increase in the electrical conductivity, free electron concentration and concentration of shallow donors. A model that explains these changes by the displacement of Ag ions into interstitial sites due to lattice deformation forces is proposed. The formation of an Ag-donor impurity band in n-ZnSe:Zn:Ag crystals stored at room temperature is also studied.

Shubnikov-de Haas (SdH) effect and magnetoresistance measurements of single crystals of diluted II-V magnetic semiconductors (Cd1-x-y Zn x Mn y )3As2 (x + y = 0.4, y = 0.04 and 0.08) are investigated in the temperature range T = 4.2 ÷ 300 K and in transverse magnetic field B = 0 ÷ 25 T. The values of the cyclotron mass m c, the effective g-factor g*, and the Dingle temperature T D are defined. In one of the samples (y = 0.04) a strong dependence of the cyclotron mass on the magnetic field m c(B) = m c(0) + αB is observed. The value of a phase shift close to β = 0.5 indicates the presence of Berry phase and 3D Dirac fermions in a single crystals of (Cd1-x-y Zn x Mn y )3As2 in one of the samples (y = 0.08).

The results of a detailed study of magnetic properties and of the microstructure of SiMn films with a small deviation from stoichiometry are presented. The aim was to reveal the origin of the high temperature ferromagnetic ordering in such compounds. Unlike SiMn single crystals with the Curie temperature ~30 K, considered Si1−x Mn x compounds with x = 0.5 +Δx and Δx in the range of 0.01–0.02 demonstrate a ferromagnetic state above room temperature. Such a ferromagnetic state can be explained by the existence of highly defective B20 SiMn nanocrystallites. These defects are Si vacancies, which are suggested to possess magnetic moments. The nanocrystallites interact with each other through paramagnons (magnetic fluctuations) inside a weakly magnetic manganese silicide matrix giving rise to a long range ferromagnetic percolation cluster. The studied structures with a higher value of Δx ≈ 0.05 contained three different magnetic phases: (a)—the low temperature ferromagnetic phase related to SiMn; (b)—the above mentioned high temperature phase with Curie temperature in the range of 200–300 K depending on the growth history and (c)—superparamagnetic phase formed by separated noninteracting SiMn nanocrystallites.

A dynamic magnonic crystal based on a planar multiferroic structure consisting of a ferrite and a ferroelectric layers has been designed and theoretically investigated for the first time. Spatially periodic electric field applied to the ferroelectric layer turns the regular multiferroic waveguide into periodic one. An electrodynamic model of the dynamic magnonic crystal and theoretical analysis of its performance is presented.

The microwave properties of multiferroic magnonic crystals based on a width-modulated slot-line were investigated theoretically for the first time. Dispersion characteristics of spin-electromagnetic waves propagating in the heterostructures were calculated. It was shown that band gaps in the spin-electromagnetic wave spectrum are controlled with both electric and magnetic fields.

Disorder of stacking of vacant sites in the crystal structure of II3V2 compounds, including the diluted magnetic semiconductor (Zn1-xMnx)3As2 is investigated. Special attention is paid to the remanent disorder at temperatures much below the order-disorder phase transition temperature Tph. Dependences of Tph and the activation energy of hopping conductivity on composition are analysed. Good agreement is obtained between theory and experimental results for the phase transition and the hopping conductivity, occurring in two quite different temperature regions. It is suggested that the remanent structural disorder leads to generation of complex centres with a large magnetic moment and a large amount of internal spin degrees of freedom. We call these centres clusters of polarization. Conditions of freezing-in of a system of interacting clusters of polarization is analysed. A way to obtain the parameters describing these centres and their interaction is discussed.

This work presents optical, magnetic properties and quasi-equilibrium condensation processes of thin composite films based on C60-MeTPP complexes. The elemental composition, surface motphology and distribution uniformity of the elements were investigated by SEM and energy-dispersive analysis. Different results were obtained for various types of MeTPP. Photoluminescence results showed decrease of intensity with C60 adding. The temperature dependence of magnetization M(T) and the field cooling (FC) and zero-field cooling (ZFC) curves for powder samples of CuTPP and CuTPP-C60 were measured to determine the changes in the magnetic behavior. Quantum-chemical calculations were performed to elucidate the experimental results.

The electrical conductivity of (Zn1-xMnx)3As2 solid solutions with 0

(Cd1-xMnx)3As2 (CMA) is a semimagnetic n-type semiconductor with Eg approximately=-0.095 eV. Magnetic susceptibility measurements in single crystals of CMA show that in weak applied fields (H or=0.04 and is attributed to presence of large magnetic clusters in the sample. From the data of the thermoremanent magnetization it is suggested that some of them can remain up to temperatures much higher than Tf.

Temperature dependence of single vortex magnetic moment in nanosize superconducting particles is investigated in the framework of quasiclassical Eilenberger approach. Such nanoparticles can be used for preparation of high-quality superconducting thin films with high critical current density. In contrast to bulk materials where the vortex magnetic moment is totally determined by flux quantum, in nano-sized specimens (with characteristic size, D, much less than effective penetration depth, λeff) the quantization rule is violated and magnetic moment is proportional to D2/λ2eff(T). Due to strong repulsion between vortices in nanoparticles only a single vortex can be trapped in them. Because of small size of particles the screening current of the vortex is located near the vortex core where the current is quite high and comparable to depairing currents. Therefore, the superconducting electron density, ns, depends on the current value and the distance from the vortex core. This effect is especially important for superconductors having gap nodes, such as YBCO. The current dependence of ns in nanoparticles is analogous to the Volovik effect in flux-line lattice in bulk samples. The magnitude of the effect can be obtained by comparing the temperature dependence of magnetic moment in the vortex and in the Meissner states. In the last case the value of screening current is small and superconducting response to the external field is determined by London penetration depth. Because of importance of nonlinear and nonlocal effects, the quantum mechanical Eilenberger approach is applied for description of the vortex in nanoparticles. The flattening of 1/λ2eff(T) dependence has been found. A comparison of the theoretical results with experimental magnetization data in Meissner and mixed states of YBCO nanopowders has been done. The presence of nonlinear and nonlocal effects in vortex current distribution is clearly visible. The obtained results are important for the description of pining in nanostructured high-Tc thin films.

We study experimentally the electronic transport and magnetism of GaAs/InGaAs/GaAs quantum wells (QW) with remote Mn δ-layer. The 2D energy spectrum of the carriers is revealed by quantum Hall Effect measurements. The ferromagnetic ordering is evidenced by anomalous Hall Effect and direct magnetization measurements. A signature of this state is also observed on the temperature dependence of the sample resistance. The dependence of the Curie temperature, TC, on manganese content, quantum well depth, and on the spacer thickness between QW and Mn δ-layer shed light on the mechanisms of exchange interaction in such structures.

The influence of the impurities on the ratio of the cutoff parameter, ξh and the Ginzburg-Landau coherence length, ξc2, in the mixed state of high-κ s-wave superconductors is investigated in framework of the quasiclassical nonlocal Eilenberger theory. Quasiparticle scattering by impurities and lowering of the temperature reduce the value of ξh to values much less than ξc2. This is different from the prediction of the local Ginzburg-Landau theory where ξh is scaled by ξc2. Detailed comparison with the behavior of the order parameter coherence length ξ1 is done. It is found that impurities influence by different way on ξh and ξ1. The curve ξh/ξc2(B/Bc2) shifts downward with increasing of impurity scattering rate while ξ1/ξc2(B/Bc2) curve shifts upward in this case.

Effects of the order parameter symmetry on the cutoff parameter ξh (determining the magnetic field distribution) in the mixed state are investigated in framework of quasiclassical Eilenberger theory for isotropic s± and for s++ pairing symmetries of superconductors using computational methods. In s± pairing symmetry the gap function has opposite sign and equal absolute values of the electron and hole pockets of the Fermi surface and in s++ pairing symmetry the gap function has the same sign of the electron and hole pockets of the Fermi surfaces. The s± pairing symmetry results in different effects of intraband (Γ0) and interband (Γπ) impurity scattering on ξh. It is found that ξh/ξc2 decreases with the Γ0 leading to values much less than those predicted by the analytical Ginzburg-Landau (AGL) theory for high Γ0. At very high Γ0 the interband scattering suppresses ξh/ξc2 considerably less than the one in the whole field range making it flat. If Γ0 and Γπ are small and equal then the ξh/ξc2(B/Bc2) dependence behaves like that of the AGL model and shows a minimum with value much more than that obtained for s++ superconductors. With high Γπ the dependence of ξh/ξc2(B/Bc2) resides above the AGL curve. Such behavior is quite different from that in s++ pairing symmetry where intraband and interband scattering rates act in a similar way and ξh/ξc2 decreases monotonously with impurity scattering and resides below the AGL curve.

Influence of impurities on coherence length Ξh in the mixed state of s-wave superconductors is investigated in framework of quasiclassical Eilenberger theory. The increasing of impurity scattering rate results in decreasing of Ξh. The obtained field dependence of Ξh for clean superconductors has a minimum and it is similar to that in Hao-Clem and Miranovic-Ichioka-Machida theories for order parameter of coherence length. It is found that growing behavior of Ξh with magnetic field in dirty superconductors is different from order parameter coherence length determining by pairing potential near with vortex core. The magnetic field dependence of coherence length in normalized units, Ξh/Ξc2(B/Bc2), is nonuniversal and depends on impurity scattering potential.

The resistivity, , is investigated in ceramic La1-xSrxMn1-yFeyO3 samples with x = 0.3 and y = 0.03  0.25 at temperatures T ~ 5  310 K in magnetic fields B up to 8 T. The metallic conductivity at y = 0.03 and the variable-range hopping (VRH) conductivity between y = 0.15  0.25 are observed. The Mott VRH conductivity takes place in all investigated samples with y ≥ 0.15 in different temperature intervals. In addition, at y = 0.25 the interval of the Shklovskii- Efros VRH conductivity, characteristic of the Coulomb gap in the density of the localized states (DOS), is observed. Analysis of the VRH conductivity yields the values of the microscopic parameters, including the DOS features and the localization radii of charge carriers.

Low-field (B = 10 G – 1 kG) magnetic properties are investigated in ceramic samples of La1–xSrxMn1−yFeyO3 (LSMFO) with x = 0.3 and y = 0.15, 0.20 and 0.25. A substantial decrease of the ferromagnetic (FM) Curie temperature, TC, with increasing y is observed, which is connected to breaking of the FM double-exchange interactions by doping with Fe. Strong magnetic irreversibility at B = 10 G gives evidence for a frustrated magnetic state of LSMFO. The asymptotic Curie-Weiss behaviour of the magnetic susceptibility, χ (T), observed well above TC, yields the values of the effective Bohr magneton per magnetic ion, exceeding considerably those of single ions. Critical behaviour of χ (T) ~ (T/TC – 1) −γ is influenced at y = 0.15 and 0.20 by a percolative (γ ≈ 1.8) and non-percolative or Heisenberg (γ ≈ 1.4) spin systems. At y = 0.25 the percolative contribution to χ (T) is not observed. The low-field magnetic properties above can be explained by the phase separation effect or generation of nanosize FM particles in the paramagnetic host matrix of LSMFO.

Quasiclassical Eilenberger equations are solved for s±-wave superconductors in the mixed state. This symmetry has been proposed for multiband superconductors as pnictides. This mechanism can be realized because of Umklapp scattering between the electron and the hole Fermi surface pockets resulting in opposite sign of pairing gap in these pockets. The applicability of the phenomenological Hao-Clem theory is investigated. Magnetic, temperature and impurity scattering rate dependencies of vortex core size are calculated. It is found that the accuracy of the effective London model gets better with the presence of the impurity scattering and even near the second critical field it is below 6%. The model with the parameters of intraband and interband impurity scattering, describing well superfluid density in BaFe2As2, is also considered.

The temperature dependence of the resistivity, ?, of ceramic La1 ? xSrxMn1 ? yFeyO3 (LSMFO) samples with x = 0.3 and y = 0.03, 0.15, 0.20 and 0.25 (or simply #03, #15, #20 and #25, respectively) is investigated between temperatures T ~ 5 and 310?K in magnetic fields B up to 8?T. Metallic conductivity in #03 is changed eventually to activated in #25. In #15 and #20 the behavior of ?(T) is more complicated, comprising of two extremes, divided by an interval of metallic behavior in #15, and two inflections of ?(T) in #20 within similar intervals ?T below ~ 100?K. Mott variable-range hopping (VRH) conductivity is observed in #15 above the ferromagnetic Curie temperature, TC. In #20 the Mott VRH conductivity takes place in three different temperature intervals at T > TC, T close to TC and T < TC. In #25, the Mott VRH conductivity is observed in two different intervals, above and below TC, divided by an intermediate interval of the Shklovskii?Efros VRH conduction regime. Analysis of the VRH conductivity yielded the values of the localization radius, ?, and the dependence of ? and of the density of the localized states, g, near the Fermi level, on B. Above TC the localization radius in all samples at B = 0 has similar values, ??1.0?1.2??, which is enhanced to ??3.3?? (#20) and 2.0?? (#25) below TC. The sensitivity of ? and g to B depend on y and T. The complicated behavior of the mechanisms of the hopping charge transfer, as well as of the microscopic parameters ? and g, is attributable to different electronic and magnetic phases of LSMFO varying with temperature and Fe doping.

Magnetoresistance (MR) of single crystals of the group II–V semiconductor n-CdSb doped with In is investigated in magnetic fields B up to 7 T and temperatures T between 1.2 and 2.4 K under hydrostatic pressure p = 0–10 kbar. Shubnikov–de Haas (SdH) oscillations of MR observed up to B ~ 4 T are characterized by a single period, giving evidence for one participating group of conduction band electrons. Pressure dependence of the SdH period and concentration reveal a second group of charge carriers, connected to a resonance impurity band with delocalized states. The SdH amplitude, A, exhibits non-universal behavior attributable to its sensitivity to scattering mechanism at low quantum numbers. The parameters characterizing the non-universality of A(T) and the pressure dependence of the cyclotron effective mass, mc(p), and of the concentration of conduction electrons, nSdH, are given. The dependences of mc and the Fermi energy on pressure are consistent with Kane-type non-parabolicity of the conduction band.

Homogeneous crystals of diluted magnetic semiconductor solid solution Zn0.9Cd0.1GeAs2 doped with 0, 1.13 and 2.65 mass% of Mn were synthesized. The grown crystals were characterized by atomic absorption and synchrotron x-ray powder diffraction analyses showing that the lattice parameter of the sample crystals are closely related to GaAs. Measurements of magnetic and transport properties were performed in the temperature range of 4–400 K using steady and pulsed magnetic fields up to B = 50 and 150 kG, respectively. The ferromagnetic Curie temperature of the sample crystals was found to be about 350 K. The magnetic ordering is attributed to the presence of MnAs clusters with mean size ~3.8 nm in the ferromagnetic phase. Influence of paramagnetic Mn2+ ions on magnetic properties of the crystals was observed only at low temperatures and was explained by the p–d interaction between charge-carrying holes and localized Mn moments.