Magnetoresistance and Quantum Oscillations in WTe2 Semimetal

Physics of the Solid State - The discovery of extreme magnetoresistance (MR) in nonmagnetic materials attracted attention to WTe2 semimetal. We studied MR in a single crystal of tungsten...     

Acoustic and NMR investigations of melting and crystallization of indium–gallium alloys in pores of synthetic opal matrices

The paper presents the results of studying the crystallization and melting processes of Ga–In eutectic alloys, which are embedded in opal matrices, using acoustic and NMR methods. The indium concentrations in the alloys were 4, 6, 9, and 15 at %. Measurements were performed upon cooling from room temperature to complete crystallization of the alloys and subsequent heating. It is revealed how the size effects and alloy composition influence the formation of phases with α- and β-Ga structures and on changes in the melting-temperature ranges. A difference was observed between the results obtained using acoustic and NMR methods, which was attributed to different temperature measurement conditions.     

Influence of the fractality of opal matrices on melting and crystallization of decane in pores

In this paper we present the results of studies on melting and crystallization of decane embedded in the pores of opal matrices filled with chemically pure hexadecane. In this studies measured the ultrasonic velocity by the pulse-interference method at frequencies of about 7 MHz in the temperature range 170–290 K.     

Magnetic properties of porous glass-CuO nanocomposites

The magnetization of the porous glass nanocomposite with CuO nanoparticles embedded in the pores has been studied in the temperature range from 1.8 to 350 K for different pore fillings. It has been shown that the magnetic properties of these nanocomposites depend significantly on pore filling. It has been found that, in the low-temperature range for the nanocomposite with a pore filling of 55% and for pressed CuO, the ZFC and FC susceptibilities diverge, a feature which has been almost absent in the nanocomposite with 21% filling. It has been demonstrated that the kink in the temperature dependence of magnetization, which corresponds to the paramagnetic-multiferroic phase transition, does not shift in the sample with a larger pore filling as compared to that observed in the bulk sample.     

Ionic mobility and attenuation of ultrasound in doped cerium trifluoride crystals

Dielectric properties of CeF₃ crystals doped by aluminum, erbium, and holmium were studied in the temperature range of 290–450 K and frequency range of 25 Hz-1 MHz. Cole-Cole diagrams are constructed. An equivalent circuit consisting of a resistance, capacitance and CPE element is suggested for interpretation of the obtained results. Ionic movement parameters are determined as dependent on the temperature. An acoustooptic method was used to measure ultrasound attenuation in the frequency range of 200–800 MHz.     

Magnetic and dielectric studies of multiferroic CuO nanoparticles confined to porous glass

Dc magnetization and ac electric permittivity were measured for the CuO-porous glass nanocomposite made and for pressed powder CuO. Magnetization curves showed a bend between two linear segments for both the nanocomposite and bulk cupric oxide at 230 K evidencing that the temperature of the transition from the paramagnetic into multiferroic phase did not change noticeably under nanoconfinement. Results suggested also a reduction of the temperature of the second transition into the collinear antiferromagnetic phase. ZFC and FC magnetizations were found to bifurcate for the nanocomposite and bulk CuO. The bifurcation was accompanied with peaks on ZFC magnetization.     

Acoustic studies of melting and crystallization of indium-gallium alloy in porous glass

Temperature dependences of the velocity of the longitudinal ultrasonic waves in a nanocomposite on the basis of porous glass filled with gallium-indium alloy have been measured. Acoustic anomalies due to crystallization and melting of the alloy in nanopores have been revealed for the complete and partial cooling-heating cycles. A two-step temperature hysteresis loop between the curves of the velocity change upon cooling and heating has been found, the existence of which is related to the formation in pores of two types of mixtures, with α- and β-Ga. Stabilization of β-Ga in nanopores has been observed. It was shown that the conditions of confined geometry lead to a shift to low temperature of the melting regions for both mixtures in comparison with the regions of the coexistence of the liquid and solid phases in bulk alloy.     

Drinfeld―Sokolov Reduction for Difference Lax Operators with Periodic Boundary Conditions in the Case of gl(n,C((λ-1)))

Within the framework of the method of formal dressing transformations, we construct a family of zero-curvature equations with discrete space variable for the case of the algebra gl(n,((^-1))). The equations obtained admit reduction with respect to the gauge group and, on the quotient, give rise to the $n$th order scalar difference equations that can be regarded as discrete analogs of KdV-equations. It is proved that the flows orresponding to different equations of the family commute. Bibliography: 10 titles.     

Poisson structures and integrable systems connected with graphs

Completely integrable systems related with graphs of a specific type are studied by the r-matrix method. The phase space of such a system is the space of connections on a graph. The nonlinear equations under consideration are Hamiltonian with respect to the Poisson bracket depending on the geometry of the graph and other structures. It is essential that the Poisson bracket be nonultralocal. An involute family of motion integrals is constructed. Explicit formulas for solutions of evolution equations are obtained in terms of solutions of a factorization problem. In the case of the group of loops, a polynomial anzatz for the Lax operator compatible with the Poisson bracket is constructed. Bibliography: 8 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 224, 1995, pp. 279–299. Translated by B. M. Bekker.     

Elastic anomalies at phase transitions in multiferroics

The temperature dependences of the elastic modulus in multiferroics-magnetoelectrics are analyzed, in which magnetic and ferroelectric orderings appear as the result of two successive phase transitions. The analytical relationships for the elastic modulus near the phase transitions to ordered states are obtained for the cases of either linear-quadratic or biquadratic contributions to magneto- and electroelastic coupling. The explicit dependence of the elastic modulus in the multiferroic phase on the magnetoelectric coupling constant was found. It is shown that the characteristic elastic properties in multiferroics can be treated using the Landau theory without taking into account fluctuations. The analysis includes changes in the phase diagrams due to the magneto- and electroelastic coupling.