Ultrasonic attenuation in superconducting niobium

Ultrasonic attenuation in superconducting niobium

Vol. 5, No. 7 8. ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS ULTRASONIC ATTENUATION IN SUPERCONDUCTING NIOBIUM N. Tsuda and T. Suzuki (Th...

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Vol. 5, No. 7 8.

ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS

ULTRASONIC ATTENUATION IN SUPERCONDUCTING NIOBIUM N. Tsuda and T. Suzuki (The Institute for Solid State Physics, Tokyo University Azabu, Minatoku, Tokyo, Japan)

A study of ultrasonic attenuation using longitudinal waves of 30 Mc/s was carried out for superconducting niobium, whose resistance ratio varied from 100 to 830. The measured temperature dependence of a~/CLD was found to deviate from the BCS relation with increasing purity, when qi < 1. A similar deviation was also found for the magnetic field dependence of CL, /a,. These results cannot be explained by an anisotropic or a two gap model. (Received 2 December 1966) (Revised 9 May 1967)

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groupe ces dipoles par rangées ou par plans. On trouve un champ qui décroft exponentiellement avec la distance du groupement et on peut se limiter aux groupements premiers voisins. On applique cette méthode au calcul de 1’ énergie d’une paroi a 180° dans la phase ferroelectrique tetragonale du Titanate de Baryum. Electric fields due to periodic arrays of point dipoles are easily calculated when dipoles are gathered into rows or planes. It is found that field decreases exponentially with the distance. Thus it Is sufficient to take into account nearest neighbours only. This method is applied to the calculation of a 180° wall energy in the Baryum Titanate tetragonal ferroelectric phase. (Received 15 May 1967)

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SPECIFIC HEAT AND HALL EFFECT MEASUREMENTS ON Cr-Mo ALLOYS B. S. Shabel and K. Schr(ider (Department of Chemical Engineering and Metallurgy, Syracuse University, Syracuse, New York)

The specific heat C2 of Chromium-molybdenum alloys containing 25 to 80 at % molybdenum was measured between 125 and 625°K. C could be separated into lattice, dilatational and’ electronic terms. Alloys with 25 and 50 at % molybdenum had electroi4c specific heats which agreed within experimental accuracy with the values pure chromium. Alloys withwhich 80 and 75 at %for molybdenum had lower values, were practically the same as those for pure molybdenum. The Hall coefficients RH of the alloys were nearly composition independent at room temperature. RH varied only between 11. 5 to 12. 7 x 10~V -cm/A-Oe. The liquid N 2 temperature values of RH were slightly lower, but also positive. (Received 1 December 1966) (Revised 26 May 1967) 10.

CALCUL DES ENERGIES DE PAROI DANS LE TITANATE DE BARYUM G. Fontaine (Laboratoire de Physique du Solide, Faculté des Sciences, 91 Orsay)

Le champ dlectrique créé par une distributton périodique de dipOles ponctuels, se calcule facilement en un point quelconque quand on

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TEMPERATURE DEPENDENCE OF THE ZERO-PHONON 415 mj~xLINE IN DIAMOND A. Halperin and 0. Nawi (Physics Department, The Hebrew University of Jerusalem, Jerusalem, Israel)

The line position, line width and the ratio (f) of the line intensity to that of the continuum were measured in the temperature range from liquid helium up to above nearly 450°K. The line shift ane line broadening were found to change with about 3).theUsing thirdthe power structure of absolute in the temperature (T 415 m.L absorption system an estimate was obtamed for the effective phonon distribution p(v) from which using formulas derived by the linear coupling theory the line shift and line broadening were calculated and were found to fit fairly wefl the experimental results. The ratio f was also calculated using the p (v) which resulted in a Debye temperature (TD) 2230°Kand a value S = 3. 7 for the most probable number of phonons involved in the broad absorption band. In this case the assumption of a Debye distribution of phonons gave S = 3.4 and TD = 1850°Kwhich agrees much better with the specific heat TD value (about 1860°K)than the values calculated using p (v). The position and width of the emission line were found to be practically the same as in absorption except for a slight deviation at the higher temperature. The f values, however, were higher for the emission line which resulted