Superconductivity as a function of carrier density and magnetic spin concentration in the SnTe-MnTe system

Superconductivity results on self doped as-cast tin telluride show a strong particle size dependence of the superconducting critical temperature (T_c, °K). The T_c of the powdered as-cast material (size ? 100μ) approaches the T_c of the pressed and sintered samples. A similar but larger effect was observed in Sn_0·87 Ag_0·10 Te, where the T_c of the as-cast material (1·8°K) decreased to about 1°K on grinding (size ? 100μ). Pressing and sintering the same material did not increase the T_c Complete T_c data on the as-cast Sn_0·97?x Ag_x Te samples with 0·01 < × < 0·16 along with their ‘pressed and sintered’ counterpart of the same composition are presented. The effect of the magnetic impurity Mn on the T_c of Sn_0·97?x?y Ag_x Mn_y Te samples was also studied by changing the parameters and the results are discussed on the basis of prevalent theories.     

Energy gap of a charge density wave in NbSe3 induced by a high magnetic field above the Peierls transition temperature

The effect of a magnetic field on the energy gap of the charge density wave (CDW) in NbSe₃ near the temperature T _p2 of the lower Peierls transition has been investigated using interlayer tunneling spectroscopy. It has been shown that the magnetic field increases the energy gap and can even induce it at temperatures higher than T _p2 by 15–20 K. As the field strength increases, the peak amplitude of the gap singularity of the tunneling spectrum first increases, reaches its maximum at 20–30 T, and then decreases. The increase in the gap peak amplitude is attributed to the field-induced improvement of the condition of the CDW nesting, while the decrease in the amplitude in high fields, to the breakdown of the ground state caused by its Zeeman splitting.     

The thermopower of amorphous CuTi-alloys as a function of concentration and temperature

We report on thermopower measurements of several Cu_100–x Ti _x -alloys (x=30, 35, 40, 45, 50, 55, 60 and 65) in the temperature range from 4.4 to 320 K. In all cases the thermopower is positive. It shows a strong variation with concentration. An analysis of the temperature dependence is presented at low and high temperatures. The correlation of the thermopower with the pressure dependence of the electrical resistivity and the Hall-coefficient is discussed and compared with theoretical predictions.We wish to dedicate this article to the memory of A.B. Bhatia who died on September 27, 1984     

Movement of liquid gallium dispersing low concentration of temperature sensitive magnetic particles under magnetic field

In this work, a temperature sensitive functional fluid was synthesized, and then its movement under the influence of magnetic field was investigated. Silica coated FeNbVB particles, prepared by chemical synthesis, were dispersed into liquid gallium, because they have a relatively high magnetization and a high temperature dependency. The synthesized functional fluid (solid fraction of 0.3 mass%) showed temperature dependence for magnetization within the testing temperature range between 298 and 353 K. The movement of gallium based fluid under the influence of the magnetic field with a magnetic field gradient was observed at various temperatures. We found that at 318 K, fluid displacement of the synthesized functional fluid is better when compared with the fluid displacement at 348 K.     

Time and field dependence of excess carrier concentration in semiconductors

The time and space distribution of excess carriers in semiconductor devices is derived through the solution of the ambipolar continuity equation. Both build-up of excess carriers due to external excitation and their decay following its termination are presented. A detailed solution for a 1-D photoconductive device with various boundary conditions is obtained. The solution is expanded to the 3-D distribution, where an analytical solution is given for the diffusion region of photodiodes. The procedure for solving the 3-D problem in photoconductor devices is outlined. The derived equations are used to demonstrate the advantages of the “covered electrodes” structure and in order to obtain an accurate value for the ambipolar mobility as measured in a four-probe device.     

Singularities in critical properties of superconductive superlattices as a function of magnetic field

The critical temperature singularities as a function of both magnetic field direction and value in periodic superconductive structure in metals have been predicted. The different types of lattices, modulation value (weak or strong), relation between characteristic magnetic length and lattice periods have been investigated on the basis of microscopic equations.     

Finite temperature gluonic gas in a magnetic field

The thermodynamical potential of a neutral gluonic plasma without quarks placed in an external abelian magnetic field is calculated, including its imaginary part, within the one-loop approximation of the temperature Green function method using the proper-time representation. The tachyonic instability of the system is discussed. A temperature at which the magnetic field stabilizes through a phase transition is estimated.     

Relaxation times in paramagnetically doped agarose gels as a function of temperature and ion concentration

Tissue equivalent gels of NMR phantoms have been investigated at 3.4 MHz. The proton T1 and T2 relaxation times have been measured in Ni++ and Cu++ doped agarose gels as a function of temperature and ion concentration. Ni-agarose gels have the lower T1 temperature dependence, but gels containing both Cu++ and Ni++ can be produced for which T1 has virtually no temperature dependence.