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Superconductivity of lanthanum and lanthanum compounds at zero and high pressure
Vol.4, No.11
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
the exact development of the potential. The results combined with those of another series of isostructural compounds, are discussed from the point of view of the electrostatic hypothesis. (Received 21 July 1966) (Revised 26 September 1966) 18.
hexane, and cyclohexanol over extended temperature ranges that encompass both the rotational and the non-rotational forms of these solids. In the case of cyclohexane and cyclohexanol the velocity of longitudinal waves near the melting point is practically the same for the liquid and for the longitudinal velocity jumps by 30 to 50 percent in going from the rotational to the nonrotational form at the transition point. Values of the elastic constants for the rotational forms of camphene and cyclohexane are deduced from the velocities, and the mean adiabatic compressibilities are calculated. The results for camphene are in agreement with the independently measured isothermal compressibility. Debye temperatures are calculated from the velocities at different temperatures for rotational and nonrotational forms of all three substances. The Debye temperatures for the rotational forms of camphene and cyclohexane are low and lie in the neighborhood of 50°K; those for the rotational and non-rotational forms of cyclohexanol are in agreement with previously published values obtained from the specific heats. Incidental to this work, the densities of the three substances in both rotational and non-rotational forms were measured over large temperature ranges. (Received 5 July 1966) 19.
about 2 x 10 18 free carriers, apparently due to anion vacancies. (Received 1 August 1966) (Revised 26 September 1966) 20.
ULTRASONIC INVESTIGATION OF SOLID di-CAMPHENE, CYCLOHEXANE AND CYCLOHEXANOL J. R. Green and C. E. Scheie (The University of New Mexico, Athuquerque, New Mexico)
The velocity of longitudinal and transverse ultrasonic waves has been measured in polycrystallirie samples of dl-camphene, cyclo-
SOME ELECTRICAL PROPERTIES OF THE SEMICONDUCTOR Ga2 03 M. R. Lorena, J. F. Woods and R. J. Gambino (IBM Watson Research Center Yorktown Heights, New York) ~-
The wide-band gap semiconductor ~ Ga2 03 has an electron mobility of the order of 100 cm 2/ V-sec at room temperature. Single crystals grown under reducing conditions have
lxxix
SUPERCONDUCTIVITY OF LANTHANUM AND LANTHANUM COMPOUNDS AT ZERO AND HIGH PRESSURE T. F. Smith and H. L. Luo (Department of Physics and the Institute for the Study of Matter Univerisity of California, San Diego; La Jolla, California 92037)
The superconducting transition temperature (Ta) of the compounds La3A1, La3 Ga, LaZn and LaMg2 are reported. The pressure dependence of the T~of a number of lanthanum compounds for which the lanthanum is considered to play the dominant role in determining the occurrence of superconductivity, has been measured. The data obtained suggest a strong correlation between the La-La nearest neighbour atomic separation and the T~with a maximum T, at an optimum separation of 3. 551. (Received 18 July 1966) (Revised 28 September 1966) 21.
A COMPARISON OF VIRIAL COEFFICIENTS OBTAINED FROM SHOCK AND ULTRASONIC DATA FOR Al AND Cu. A. L. Ruoff (Department of Materials Science and Engineering, Cornell University, Ithaca, New York)
It is shown here that ultrasonic virial coefficients a and b obtained by the method of least squares, are in good agreement with the virial coefficients obtained from shock data (also obtained by least squares analysis). When the same ultrasonic coefficients are obtained from a Taylor series expansion the b coefficient is always too large: for the data analyzed here, it is 27% too large for aluminum and 46% too large for copper. The reason that the Taylor coefficient are inappropriate is described. 22.
PARAMAGNETIC RESONANCE OF THE Ag~ ION IN IRRADIATED ALKALI CHLORIDES J. Sierro (Argonne National Laboratory, Argonne, Illinois and University of Geneva, Geneva, Switzerland) +
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
the exact development of the potential. The results combined with those of another series of isostructural compounds, are discussed from the point of view of the electrostatic hypothesis. (Received 21 July 1966) (Revised 26 September 1966) 18.
hexane, and cyclohexanol over extended temperature ranges that encompass both the rotational and the non-rotational forms of these solids. In the case of cyclohexane and cyclohexanol the velocity of longitudinal waves near the melting point is practically the same for the liquid and for the longitudinal velocity jumps by 30 to 50 percent in going from the rotational to the nonrotational form at the transition point. Values of the elastic constants for the rotational forms of camphene and cyclohexane are deduced from the velocities, and the mean adiabatic compressibilities are calculated. The results for camphene are in agreement with the independently measured isothermal compressibility. Debye temperatures are calculated from the velocities at different temperatures for rotational and nonrotational forms of all three substances. The Debye temperatures for the rotational forms of camphene and cyclohexane are low and lie in the neighborhood of 50°K; those for the rotational and non-rotational forms of cyclohexanol are in agreement with previously published values obtained from the specific heats. Incidental to this work, the densities of the three substances in both rotational and non-rotational forms were measured over large temperature ranges. (Received 5 July 1966) 19.
about 2 x 10 18 free carriers, apparently due to anion vacancies. (Received 1 August 1966) (Revised 26 September 1966) 20.
ULTRASONIC INVESTIGATION OF SOLID di-CAMPHENE, CYCLOHEXANE AND CYCLOHEXANOL J. R. Green and C. E. Scheie (The University of New Mexico, Athuquerque, New Mexico)
The velocity of longitudinal and transverse ultrasonic waves has been measured in polycrystallirie samples of dl-camphene, cyclo-
SOME ELECTRICAL PROPERTIES OF THE SEMICONDUCTOR Ga2 03 M. R. Lorena, J. F. Woods and R. J. Gambino (IBM Watson Research Center Yorktown Heights, New York) ~-
The wide-band gap semiconductor ~ Ga2 03 has an electron mobility of the order of 100 cm 2/ V-sec at room temperature. Single crystals grown under reducing conditions have
lxxix
SUPERCONDUCTIVITY OF LANTHANUM AND LANTHANUM COMPOUNDS AT ZERO AND HIGH PRESSURE T. F. Smith and H. L. Luo (Department of Physics and the Institute for the Study of Matter Univerisity of California, San Diego; La Jolla, California 92037)
The superconducting transition temperature (Ta) of the compounds La3A1, La3 Ga, LaZn and LaMg2 are reported. The pressure dependence of the T~of a number of lanthanum compounds for which the lanthanum is considered to play the dominant role in determining the occurrence of superconductivity, has been measured. The data obtained suggest a strong correlation between the La-La nearest neighbour atomic separation and the T~with a maximum T, at an optimum separation of 3. 551. (Received 18 July 1966) (Revised 28 September 1966) 21.
A COMPARISON OF VIRIAL COEFFICIENTS OBTAINED FROM SHOCK AND ULTRASONIC DATA FOR Al AND Cu. A. L. Ruoff (Department of Materials Science and Engineering, Cornell University, Ithaca, New York)
It is shown here that ultrasonic virial coefficients a and b obtained by the method of least squares, are in good agreement with the virial coefficients obtained from shock data (also obtained by least squares analysis). When the same ultrasonic coefficients are obtained from a Taylor series expansion the b coefficient is always too large: for the data analyzed here, it is 27% too large for aluminum and 46% too large for copper. The reason that the Taylor coefficient are inappropriate is described. 22.
PARAMAGNETIC RESONANCE OF THE Ag~ ION IN IRRADIATED ALKALI CHLORIDES J. Sierro (Argonne National Laboratory, Argonne, Illinois and University of Geneva, Geneva, Switzerland) +