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The possibility observation of the electric field controlled multicaloric response through quasi-isostatic compression as a result of the converse piezoelectric effect was demonstrated on the cylindrical type magnetoelectric composite MnAs/PZT. It was shown that an electric voltage of 100 V corresponding to an electric field of E ∼0.3 kV/mm applied to the walls of the piezoelectric component PZT of the MnAs/PZT composite contributes to an increase in the maximum adiabatic temperature change by 0.2 K in the temperature range of the magnetostructural phase transition of MnAs ∼317 K at a magnetic field change of 1.8 T. Numerical analysis using the finite element method has shown that an electric field voltage of 100 V is capable of creating a quasi-isostatic mechanical stress in the region inside a cylindrical PZT tube of ∼3 MPa. Moreover, in the region of weak pressures up to 10 MPa, the contribution to the total adiabatic temperature change from piezo-mechanical compression linearly depends on the electrical voltage that can be used for control by magnetic and caloric properties of multicaloric materials. [ABSTRACT FROM AUTHOR]

We present the results of direct measurements of the adiabatic temperature change (ΔTad) for the Fe50Rh50 alloy in a cyclic magnetic field (CMF) of 1.2 T. It is shown that increasing the frequency of the CMF from 1 to 30 Hz is accompanied by a shift of the position of temperature dependence ΔTad(T) maximum, Tmax, toward low temperatures. With an increase in the CMF frequency from 1 to 5 Hz, the ΔTmax value decreases by ∼12%. A further increase in frequency leads to stabilization of the effect. In the vicinity of the antiferromagnetic-ferromagnetic phase transition point TC = 370 K, ΔTad exhibits unconventional frequency behavior: while at T well above TC, the value of ΔTad monotonously decreases as frequency increases, at T = 370.4 K; an interval of frequency-independent ΔTad up to 10 Hz is observed, and at 368 K < T < TC, the maximum of ΔTad(f) dependence is found in the interval 1 < f < 10 Hz. Such behavior in the future can be applied in magnetic cooling technology due to large values of ΔTad and the frequency stability of the effect in alternating fields. The specific cooling power reaches giant values of ∼22 W/g at 20 Hz, which is comparable to the values under the same conditions for Gd −21.6 W/g. The unconventional behavior of ΔTad in the CMF is discussed in the context of the role of secondary phase localization, which leads to an enhanced internal local magnetic field and dynamic effects of ΔTad. [ABSTRACT FROM AUTHOR]

Direct studies of the adiabatic temperature change (ΔTad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature TC = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔTad = −12 K in 20 T at the initial temperature T0 = 275 K. The irreversible part of the MCE reached ΔTir = −10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems. [ABSTRACT FROM AUTHOR]

In cyclic magnetic fields with an amplitude of up to 8 T, the magnetocaloric effect (MCE) and thermal expansion in the Ni46Mn41In13 Heusler alloy are investigated. The magnetic and structural contributions to the total entropy change are estimated, and it was found that the magnetic contribution is dominant and the contributions have different signs (ΔSm = 12.19 J/kg K, ΔSstr = −1.05 J/kg K). In weak magnetic fields, the values of the MCE in heating and cooling runs differ greatly, which is associated with an unequal response of the structurally and magnetically inhomogeneous system to the influence of a magnetic field. [ABSTRACT FROM AUTHOR]

In this paper, we focus on understanding the magnetic field and temperature dependences of the heat capacity CP, electrical resistivity ρ, and magnetocaloric effect ΔTad in Fe48Rh52 alloy near room temperatures. The phase diagram is constructed according to the CP(H, T) and ρ(H, T) data, and the field shift of the critical temperature is found to be 9.6 K/T. The experimental results on the heat capacity do not confirm the existing assumption about the electronic nature of the antiferromagnet–ferromagnet phase transition in the FeRh alloy. An increase in resistance through the ferromagnetic–antiferromagnetic phase transition is explained by a sharp decrease of the carrier density and simultaneously the appearance of an additional conducting channel. The adiabatic temperature change ΔTad at a field change of 1.8 T equals −9.8 K, and the maximum value of the entropy change ΔS estimated from CP(H, T) and ΔTad(H, T) data is equal to 12.8 J/kg K. The differences in the magnetocaloric effect values in the heating and cooling run in weak magnetic fields are explained based on the thermal expansion data. An almost reversible degradation of the magnetocaloric effect was discovered upon the continuous application of a cyclic magnetic field at temperatures near the magnetostructural transition. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect in the Fe49Rh51 alloy was systematically studied using three different approaches: in-field differential scanning calorimetry, standard direct measurement of the adiabatic temperature change, and a non-contact method based on a thermo-optical phenomenon, the mirage effect, which was able to directly test the magnetocaloric response induced by a fast magnetic field variation. The metamagnetic phase transition of Fe49Rh51 was studied in the temperature range of 290–330 K at magnetic fields up to 1.8 T through magnetic and calorimetric measurements. The estimated parameters of phase transition were comparable with the literature data. The values of adiabatic temperature change obtained with the three methods (calorimetry, standard direct measurement, and mirage-based technique), which explore three different time scales of the field variation (static field, 1 T s−1, 770 T s−1), were consistent, proving the absence of dynamic constraints in the first-order magnetostructural transition at the maximum field sweep rate. [ABSTRACT FROM AUTHOR]

Results of the experimental investigations of magnetocaloric effect (MCE) and magnetostriction in Pr0.7Sr0.2Ca0.1MnO3 manganite in the temperature range of 80–310 K and in magnetic fields up to 80 kOe are presented. The behavior of the MCE is characteristic of materials with magnetostructural phase transitions of the first order. Frequency (1–14 Hz) dependences of the MCE in a magnetic field of 6.2 kOe are investigated. It is shown that near TC, the ΔT dependence of the frequency f is well described by the expression: Δ T (f) = Δ T f = 0 − B f n (n = 1.53, B = 0.01185 K/Hzn). The results of the investigation of magnetostriction show that near TC, the value of magnetostriction is Δɛ = 4.49 ⋅ 10−4 in a magnetic field of 80 kOe. According to the results of the study of magnetostriction in various magnetic fields, it is shown that the change in the magnetic entropy is directly proportional to magnetostriction ΔSM = γ1Δɛ (γ1 = 2 ⋅ 104 J/kg K). This ratio can serve as another indirect method for estimating the MCE, which shows good agreement with the data of direct caloric measurements. [ABSTRACT FROM AUTHOR]

In this report, we present results of the direct measurements of the adiabatic temperature change in MnAs1−xPx compounds (x = 0, 0.02, 0.025, and 0.03) in cyclic magnetic fields up to 8 T. The substitution of As by P results in a slight shift of the Curie temperature and more notable change in the magnetocaloric effect (MCE) value. Estimations of the lattice and magnetic contributions show that in the MnAs compound, the lattice contribution dominates (about 70% of the total MCE). Substitution of As with phosphorus leads to a decrease in the total value of the MCE, which is caused by a decrease in the lattice contribution, and the magnetic contribution almost does not change in the absolute value. A reversible degradation of the magnetocaloric effect in cyclic magnetic fields is found, which restricts the application of this material to the magnetic cooling technology. [ABSTRACT FROM AUTHOR]

A series of phase separated La0.5Ca0.5MnO3 manganite samples with different grain sizes were studied by ac susceptibility, direct magnetocaloric effect (ΔT), and heat capacity measurements. The ac susceptibility shows that fractions of ferromagnetic and antiferromagnetic phases and consequently the phase separated state can be controlled by means of sintering temperature. Lower sintering temperature leads to a ferromagnetic state, while higher sintering temperature increases antiferromagnetic phase fraction, resulting in a phase separated state. In the phase separated samples, ΔT shows a conventional positive peak near TC and an anomalous positive peak at lower temperature near TN. The anomalous positive peak appears at higher magnetic field and is accompanied with thermal hysteresis. It is suggested that the anomalous magnetocaloric behaviors result from phase separation and first order magnetostructural phase transition. This study shows that direct magnetocaloric effect is a useful technique for the study of manganites. [ABSTRACT FROM AUTHOR]

We report upon the specific heat and magnetocaloric properties of Cu2MnBO5 over a temperature range of 60–350 K and in magnetic fields up to 18 kOe. It is found that at temperatures below the Curie temperature (TC ∼ 92 K), CP(T)/T possesses a linear temperature-dependent behavior, which is associated with the predominance of two-dimensional antiferromagnetic interactions of magnons. The temperature independence of CP/T = f(T) is observed in the temperature range of 95–160 K, which can be attributed to the excitation of the Wigner glass phase. The magnetocaloric effect [i.e., the adiabatic temperature change, ΔTad (T,H)] is assessed through a direct measurement or an indirect method using the CP(T,H) data. Owing to its strong magnetocrystalline anisotropy, an anisotropic magnetocaloric effect (MCE) or the rotating MCE [ΔTadrot (T)] is observed in Cu2MnBO5. A deep minimum in the ΔTadrot (T) near the TC is observed and ascribed to the anisotropy of the paramagnetic susceptibility. [ABSTRACT FROM AUTHOR]

The results of direct studies of the magnetocaloric effect (MCE) of the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in cyclic magnetic fields are presented. It is shown that in cyclic magnetic fields, the MCE value near the magnetostructural phase transition depends on the rate of temperature scanning. A higher rate of change in the sample temperature causes the MCE to have a greater value. The observed effect is explained by irreversible phase transition, induced by a magnetic field, from a low-symmetry martensitic phase to a high-symmetry austenitic phase. Moreover, it is observed only within the temperature hysteresis loop of the magnetostructural phase transition. Such materials, despite the considerable MCE values under a single application of the magnetic field, are unpromising due to a strong change in the magnetocaloric properties in cyclic magnetic fields. [ABSTRACT FROM AUTHOR]

A study of how the partial substitution of Bi with Pb impacts the mechanism of excess conductivity in a Bi-Sr-Ca-Cu-O system. It is found that such a substitution leads to an increase in the critical temperature of the Bi1.7Pb0.3Sr2Ca2Cu3Oy(B2) sample, in comparison to Bi2Sr2CaCu2Ox (B1) [Tc (B2) = 100.09 K and Tc (B1) = 90.5 K, respectively]. At the same time, the resistivity ρ of the sample B2 in the normal phase decreases by almost 1.5 times in comparison to B1. The mechanism responsible for the generation of excess conductivity in cuprate HTSCs Bi2Sr2CaCu2Ox and Bi1.7Pb0.3Sr2Ca2Cu3Oy is examined using the local pair model with consideration of the Aslamazov-Larkin theory, near Tc. The temperature T0 of the transition from the 2D fluctuation region to the 3D (i.e., the temperature of the 2D-3D crossover), is also determined. The coherence length ξc(0) along the c axis of fluctuation Cooper pairs is calculated. It is shown that the partial substitution of Bi with Pb in the Bi-Sr-Ca-Cu-O system leads to a decrease in ξc(0) by a factor of 1.3 (4.205 and 3.254 Å, respectively), and that there is a narrowing of both the region of pseudogap existence and the region of superconducting fluctuations near Tc. The temperature dependence of the pseudogap Δ*(T) and the value Δ*(Tc) are determined, and the temperatures Tm, which correspond to the maximum of the pseudogap as a function of temperature in these materials, are estimated. The pseudogap maxima in samples B1 and B2 are found to be 61.06 and 38.18 meV, respectively. [ABSTRACT FROM AUTHOR]

A study of how the partial substitution of Bi with Pb impacts the mechanism of excess conductivity in a Bi-Sr-Ca-Cu-O system. It is found that such a substitution leads to an increase in the critical temperature of the Bi1.7Pb0.3Sr2Ca2Cu3Oy(B2) sample, in comparison to Bi2Sr2CaCu2Ox (B1) [Tc (B2) = 100.09 K and Tc (B1) = 90.5 K, respectively]. At the same time, the resistivity ρ of the sample B2 in the normal phase decreases by almost 1.5 times in comparison to B1. The mechanism responsible for the generation of excess conductivity in cuprate HTSCs Bi2Sr2CaCu2Ox and Bi1.7Pb0.3Sr2Ca2Cu3Oy is examined using the local pair model with consideration of the Aslamazov-Larkin theory, near Tc. The temperature T0 of the transition from the 2D fluctuation region to the 3D (i.e., the temperature of the 2D-3D crossover), is also determined. The coherence length ξc(0) along the c axis of fluctuation Cooper pairs is calculated. It is shown that the partial substitution of Bi with Pb in the Bi-Sr-Ca-Cu-O system leads to a decrease in ξc(0) by a factor of 1.3 (4.205 and 3.254 Å, respectively), and that there is a narrowing of both the region of pseudogap existence and the region of superconducting fluctuations near Tc. The temperature dependence of the pseudogap Δ*(T) and the value Δ*(Tc) are determined, and the temperatures Tm, which correspond to the maximum of the pseudogap as a function of temperature in these materials, are estimated. The pseudogap maxima in samples B1 and B2 are found to be 61.06 and 38.18 meV, respectively. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect (MCE) in an Fe48Rh52 alloy and Sm0.6Sr0.4MnO3 manganite was studied in cyclic magnetic fields. The adiabatic temperature change in the Fe48Rh52 alloy for a magnetic field change (ΔB) of 8 T and a frequency (f) of 0.13Hz reaches the highest value of (ΔTad) of -20.2K at 298 K. The magnitude of the MCE in Sm0.6Sr0.4MnO3 reaches DTad=6.1K at the same magnetic field change at 143K. The temperature regions, where a strong MCE is exhibited in an alternating magnetic field, are bounded in both compounds. In the case of the Fe48Rh52 alloy, the temperature range for this phenomenon is bounded above by the ferromagnetic to antiferromagnetic transition temperature in the zero field condition during cooling. In the case of the Sm0.6Sr0.4MnO3 manganite, the temperature range for the MCE is bounded below by the ferromagnetic-paramagnetic transition temperature in zero field during heating. The presence of these phase boundaries is a consequence of the existence of areas of irreversible magnetic-field-induced phase transitions. It is found that the effect of long-term action of thousands of cycles of magnetization/demagnetization degrades the magnetocaloric properties of the Fe48Rh52 alloy. This can be explained by the gradual decrease in the size of the ferromagnetic domains and increasing role of the domain walls due to giant magnetostriction at the ferromagnetic to antiferromagnetic transition temperature. The initial magnetocaloric properties can be restored by heating of the material above their Curie temperature. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect (MCE) in an Fe48Rh52 alloy and Sm0.6Sr0.4MnO3 manganite was studied in cyclic magnetic fields. The adiabatic temperature change in the Fe48Rh52 alloy for a magnetic field change (ΔB) of 8 T and a frequency (f) of 0.13Hz reaches the highest value of (ΔTad) of -20.2K at 298 K. The magnitude of the MCE in Sm0.6Sr0.4MnO3 reaches DTad=6.1K at the same magnetic field change at 143K. The temperature regions, where a strong MCE is exhibited in an alternating magnetic field, are bounded in both compounds. In the case of the Fe48Rh52 alloy, the temperature range for this phenomenon is bounded above by the ferromagnetic to antiferromagnetic transition temperature in the zero field condition during cooling. In the case of the Sm0.6Sr0.4MnO3 manganite, the temperature range for the MCE is bounded below by the ferromagnetic-paramagnetic transition temperature in zero field during heating. The presence of these phase boundaries is a consequence of the existence of areas of irreversible magnetic-field-induced phase transitions. It is found that the effect of long-term action of thousands of cycles of magnetization/demagnetization degrades the magnetocaloric properties of the Fe48Rh52 alloy. This can be explained by the gradual decrease in the size of the ferromagnetic domains and increasing role of the domain walls due to giant magnetostriction at the ferromagnetic to antiferromagnetic transition temperature. The initial magnetocaloric properties can be restored by heating of the material above their Curie temperature. [ABSTRACT FROM AUTHOR]

We examine the effect of replacing calcium by zinc has on the transport properties of the BiSrCaCuO-2221 system. It is shown that the critical temperatures Tc of the Bi2Sr2CaCu2Ox(B1) and Bi2Sr2ZnCu2Oy(B2) samples are close (81K and 80.72 K). However, the resistivity ρ of the Bi2Sr2ZnCu2Oy sample increases considerably, and the ratio ρB2/ρB1≈10 at 100 K. We use the local pair model to analyze the mechanism behind the formation of excess conductivity in Bi2Sr2CaCu2Ox and Bi2Sr2ZnCu2Oy(B2), with consideration of the Aslamazov-Larkin theory near Tc. We determined the temperature T0 of the transition from the 2D fluctuation area to the 3D region (i.e., the 2D-3D crossover temperature). We calculated the coherence length of the fluctuation Cooper pairs along the c axis, ξc(0). It is shown that substituting Zn for Ca reduces ξc(0) by almost 1.5 times (4.8 Å and 3.3 Å, respectively), and also leads to a narrowing of both the pseudogap region and the superconducting fluctuation area near Tc. We determined the temperature dependence of the pseudogap Δ*T and Δ*(Tc). The increase of ρ, its specific temperature dependence and the significant decrease of T* in sample B2, all point to the destruction of local pairs at all high temperatures, i.e., to the suppression of the pseudogap by Zn doping. [ABSTRACT FROM AUTHOR]

Theoretical as well as numerical analyses of the full set of Maxwell's equations is carried out to study non-axisymmetric (m≠  0) guided modes in radially nonuniform helicon (HE) discharges. Unlike the axisymmetric (m = 0) modes, these modes reveal a non-reciprocal behavior with respect to the azimuthal direction. We develop the conditions for propagation and non-propagation of the various modes in the helicon parameter range, thereby focussing on the important role of the radial density gradient. Three types of modes occurring in different parameter ranges are described, i.e., the helicon (HE) mode, the electrostatic (ES) or Trivelpiece-Gould mode, and the locally coupled (LC) mode that is characterized by mode coupling (MC) in a certain region of the plasma density profile. In contrast to m=+1 modes, the parameter range of m=−1 modes is much more restricted as rather high densities are needed for the propagation of the helicon and LC modes. An important issue of the investigations is the rf power coupling and absorption via the various modes. Computations based on a simple antenna-plasma model show that the axial wavenumber of the antenna determines decisively which type of mode is excited. In case of LC mode excitation, the dominant role of the MC layer for the absorption is demonstrated. Finally, the rf power coupling to helicon modes is studied. The density limit for m=−1 helicon mode propagation and the narrow magnetic field profiles of these modes are the main reasons why the rf power absorption in helicon discharges occurs via m=+1 helicon modes. [ABSTRACT FROM AUTHOR]

Theoretical as well as numerical analysis of the full set of Maxwell's equations was carried out to study axisymmetric (m=0) as well as non-axisymmetric (m ≠ 0) guided modes in a helicon discharge (radius R). In detail, the propagation of various guided modes for conditions of strong radial inhomogeneity was treated. The m=1 helicon dispersion exhibits for kzR ≪ 1 a quadratic frequency dependence on the axial wavenumber, ω ∝ kzz, if the radial density gradient is steep enough. These modes reveal non-reciprocal behavior with respect to the azimuthal (θ) direction, that is, only modes with positive azimuthal mode numbers, m>0, can propagate. This is in contrast to the linear dispersion relation, ω ∝ kz (kzR ≪ 1), for common helicon mode propagation in weakly non-uniform plasma. The results agree reasonably with those obtained from the 2ndorder helicon wave equation derived for Ez=0. Furthermore, guided electrostatic (ES) modes were analyzed using the 2nd-order wave equation and their eigen mode spectrum was obtained. These modes reveal also non-reciprocal behavior with respect to θ and obey a quadratic dispersion law in strongly non-uniform plasma. A particular objective is mode coupling (MC) occurring when the helicon and the ES dispersion branches merge in a certain layer. For m=1 modes, mode coupling may arise at rather low density when the radial density gradient is steep enough. In any case, new modes, denoted as localized-coupled (LC) modes, may occur in the presence of an MC layer within the plasma. As for helicon and ES modes, the m=1 LC modes exhibit quadratic scaling in strongly non-uniform plasma. As a particular case, we examined the propagation of m=1 modes in a plasma column with a peaked density distribution in the center. The field distribution was found to be drastically altered due to mode coupling, thus leading to strongly enhanced wave absorption near the axis. [ABSTRACT FROM AUTHOR]

Long-lived minima are detected at Tmin1 = 275 K and Tmin2 = 252 K in the ρ(T) curve of polycrystalline CdBa2Cu3O7-δ, which has a superconducting transition at 86.8 K. It is shown that the excess conductivity Δσ(T) near Tmin obeys the classical Aslamazov-Larkin fluctuation theory. This suggests that fluctuation Cooper pairs may develop in CdBa2Cu3O7-δ at T > Tc. The experimental data are used to calculate the coherence length ξc(0), the 2D-3D crossover temperature T0, and the interplanar pairing constants. The magnitude and temperature dependence of the pseudogap for a sample without the minima are found to be typical of cuprate HTSC materials. [ABSTRACT FROM AUTHOR]

The effect of 16??→?18? isotope substitution on specific heat and magnetocaloric effect of polycrystalline La0.7Ca0.3MnO3 manganite is studied. Mainly the effect of isotope substitution for the specific heat and magnetocaloric effect is only the reduction of temperatures of anomalies. ΔTad values at magnetic field change ΔH?=?18 kOe are equal to ΔTad?=?2.41?K and 2.60?K for La0.7Ca0.3Mn16O3 (LCMO16) and La0.7Ca0.3Mn18O3 (LCMO18), respectively. The sandwich of the LCMO16 and LCMO18 samples was produced for direct measurement of ΔTad. The use of sandwich from materials with near similar magnetocaloric properties increases the relative cooling power by about 20%. [ABSTRACT FROM AUTHOR]

A new superconducting ceramic material CdBa2Cu3O7-δ is obtained. It is found that the superconducting transition (at 86 K) is retained when yttrium is fully replaced by cadmium in the Y-Ba-Cu-O system. X-ray diffraction studies show that the crystalline structure is unchanged and the identified peaks coincide when Y is replaced by Cd in YBa2Cu3O7-δ. Besides a stable superconducting transition, a phase transition near 275 K was seen in the temperature dependence of the specific resistivity which shifted toward lower temperatures (252 K) and then disappeared completely over repeated measurement cycles. The thermal conductivity k of YBa2Cu3O7-δ and CdBa2Cu3O7-δ was found to vary little with temperature up to the superconducting transition. Substituting Cd for Y in the initial HTSC material led to a substantial increase in the lattice thermal conductivity. Measurements of the thermal emf showed that it is positive in YBa2Cu3O7-δ and negative in CdBa2Cu3O7-δ. [ABSTRACT FROM AUTHOR]

The specific heat, thermal diffusivity, and thermal conductivity of ceramic samples of Nd0.55Sr0.45MnO3, Sm0.55Sr0.45MnO3, and Eu0.55Sr0.45MnO3 in the temperature range 20–350 K have been measured. Anomalies due to magnetic phase transitions have been observed and are interpreted. The temperature dependence of the free-path length is traced. The dependence of the measured coefficients on the degree of cationic disorder due to the difference of the radii of the A cations is determined. [ABSTRACT FROM AUTHOR]

The specific heat, thermal diffusivity, and thermal conductivity of ceramic samples of Nd0.55Sr0.45MnO3, Sm0.55Sr0.45MnO3, and Eu0.55Sr0.45MnO3 in the temperature range 20–350 K have been measured. Anomalies due to magnetic phase transitions have been observed and are interpreted. The temperature dependence of the free-path length is traced. The dependence of the measured coefficients on the degree of cationic disorder due to the difference of the radii of the A cations is determined. [ABSTRACT FROM AUTHOR]

An investigation of the critical behavior of the specific heat of the manganites La1-xAgxMnO3 ×(x=0.1,0.15,0.2) near the Curie temperature is carried out. The behavior of the universal critical parameters near the phase transition point is established. All of the samples studied correspond to the ferromagnetic Heisenberg 3D universality class of critical behavior, with the critical exponent α=-0.115, -0.106, and -0.106 for La0.9Ag0.1MnO3, La0.85Ag0.15MnO3, and La0.8Ag0.2MnO3, respectively. It is shown that the universality class of the critical behavior of the specific heat of the manganites La1-xAgxMnO3 is independent of the silver concentration. [ABSTRACT FROM AUTHOR]

The oblique wave propagation in helicon-sustained plasma accounting for the effect of the radial electron density gradient is investigated. It is shown that the conditions for the conversion of electrostatic and electromagnetic modes may change drastically in strongly nonuniform helicon plasma due to modification of the wave dispersion branches. Furthermore, the densities at which mode conversion occurs can be considerably lower if the density gradient is steep enough. This result contrasts with the common mode conversion theory neglecting density gradient effects and predicting mode conversion in the central plasma region at very high electron densities. [ABSTRACT FROM AUTHOR]

A comprehensive investigation of the electro- and thermophysical properties of the manganite La0.8Ag0.15MnO3 is carried out over a wide temperature interval (4.2–350 K) and in magnetic fields up to 26 kOe. It is shown that the colossal magnetoresistance in a magnetic field of 11 kOe amounts to 57%, and the effect is maximum at room temperature. The dominant mechanisms of current carrier scattering in the ferromagnetic and paramagnetic phases are established. An analysis of the data on the low-temperature heat capacity provides estimates of the electronic density of states at the Fermi level, NF=6.82×1024 eV-1 mol-1, and of the Debye temperature, θD=370 K. The results of thermal expansion measurements are used to find the spontaneous magnetostriction. It is found that the phonon mechanism of heat transfer is dominant, and the local Jahn–Teller distortions are considered as the main mechanism of phonon scattering. [ABSTRACT FROM AUTHOR]

Parametric instabilities arising in the pump field of a helicon wave are analyzed for typical parameters of helicon-produced plasmas. The pump wavenumber parallel to the magnetic field is assumed to be finite according to recent experimental findings obtained on a high-density helicon discharge. The parametric decay of the helicon pump wave into ion-sound and Trivelpiece–Gould waves is investigated. The approach takes into account that the damping rate of the Trivelpiece–Gould wave is generally much higher than the ion-sound frequency. The theoretical results are in agreement with the growth rates and thresholds of this instability, as well as the dispersion properties of the decay waves observed in helicon experiments. Estimates of the level of the decay parametric turbulence turn out to be sufficiently high to account for the strong absorption observed in helicon-produced plasmas. [ABSTRACT FROM AUTHOR]

It is demonstrated that the magnetization current, which arises from the interaction of high-frequency electromagnetic waves with hot collisionless, unmagnetized electron plasmas, can be derived by means of the ten-moment system of hydrodynamic equations. It is pointed out that the magnetization current is solely associated with the thermal motion of the electrons, and that it therefore does not appear in cold plasmas. This expression for the magnetization current agrees with those derived previously from kinetic theory. The present derivation provides, however, a comparatively much clearer physical picture of the origin of this current. In the limit where the phase velocity is much larger than the electron thermal velocity, a new result for the high-frequency induced vorticity of the plasma is obtained. It is also shown that the magnetization current in this paper is responsible for a novel scattering mechanism in which the high-frequency electromagnetic waves are scattered off vortex motions. [ABSTRACT FROM AUTHOR]

Discusses how the electron heating of radio frequency gas discharges is treated on the basis of quasilinear kinetic theory for characteristic scale lengths of the heating field much shorter than the electron mean free path. Consideration of plasmas bounded by walls providing specular reflection; Expressions for the coefficients of electron diffusion in energy space.

Presents a fluid model of surface wave that produced discharges for diffusion controlled regimes, taking into account simultaneously nonlinear contributions from stepwise ionization and volume recombination. Effect of saturation of metastable densities with growing electron density; Charged particle continuity and energy balance equations.

Direct measurements of the magnetocaloric effect in samples of rapidly quenched ribbons of Mn50Ni40In10 and Ni50Mn37Sn13 Heusler alloys with potential applications in magnetic refrigeration technology are carried out. The measurements were made by a precise method based on the measurement of the oscillation amplitude of the temperature in the sample while is subjected to a modulated magnetic field. In the studied compositions both direct and inverse magnetocaloric effects associated with magnetic (paramagnet-ferromagnet-antiferromagnet) and structural (austenite-martensite) phase transitions are found. Additional inverse magnetocaloric effects of small value are observed around the ferromagnetic transitions. [ABSTRACT FROM AUTHOR]

The composition of synthesized ceramic samples is investigated by x-ray phase analysis, and it is established that they are high-Tc superconducting Bi2Sr2ZnCu2Ox. It is found that the crystal structure is preserved. To investigate how the superconductivity of Bi–Sr–Ca–Cu–O is influenced by the substitution of calcium by zinc, measurements of the temperature dependence of the resistivity, thermal conductivity, and thermopower (Siebeck coefficient) are carried out. It is found that the substituted compound Bi2Sr2ZnCu2Ox retains its superconducting properties (T0=82 K). It is shown that substitution of Ca by Zn leads to an increase of the thermal conductivity. While the thermopower of Bi2Sr2CaCu2Ox shows p-type conductivity in the whole range of temperatures investigated, in Bi2Sr2ZnCu2Ox the type of the conductivity is changed to n-type. [ABSTRACT FROM AUTHOR]

A study of the influence of magnetic field on the thermal conductivity of Bi2Sr2CaCu2Ox is made. It is found that the thermal conductivity increases under the influence of magnetic field because the electronic part of the thermal conductivity increases on account of breaking of the Cooper pairs and a decrease of the phonon-vortex scattering. [ABSTRACT FROM AUTHOR]

Samples of Sm1-xSrxMnO3 with x=0.425 and 0.450 are investigated experimentally at temperature of 77 K in pulsed and static electric E and magnetic H (up to 10 kOe) fields in the mutual orientations H‖E and H⊥E. N-shaped current-voltage characteristics and high-frequency (up to 3 MHz) oscillations of the current are observed. [ABSTRACT FROM AUTHOR]

Samples of Sm1-xSrxMnO3 with x=0.425 and 0.450 are investigated experimentally at temperature of 77 K in pulsed and static electric E and magnetic H (up to 10 kOe) fields in the mutual orientations H‖E and H⊥E. N-shaped current-voltage characteristics and high-frequency (up to 3 MHz) oscillations of the current are observed. [ABSTRACT FROM AUTHOR]

Examines the structural dynamics of a non-neutralized charged-particle beam based on the gas dynamics description. Spatial behavior of density for beams with a finite particle temperature; Constant axial velocity along the beam trajectory.

A comprehensive investigation of the electro- and thermophysical properties of the manganite La0.8Ag0.15MnO3 is carried out over a wide temperature interval (4.2–350 K) and in magnetic fields up to 26 kOe. It is shown that the colossal magnetoresistance in a magnetic field of 11 kOe amounts to 57%, and the effect is maximum at room temperature. The dominant mechanisms of current carrier scattering in the ferromagnetic and paramagnetic phases are established. An analysis of the data on the low-temperature heat capacity provides estimates of the electronic density of states at the Fermi level, NF=6.82×1024 eV-1 mol-1, and of the Debye temperature, θD=370 K. The results of thermal expansion measurements are used to find the spontaneous magnetostriction. It is found that the phonon mechanism of heat transfer is dominant, and the local Jahn–Teller distortions are considered as the main mechanism of phonon scattering. [ABSTRACT FROM AUTHOR]