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1 Sep 1967

Volume 11, Issue 5, pp. 143-173


ENHANCEMENT OF THE MEISSNER EFFECT IN TYPE II SUPERCONDUCTORS BY A HEAT PULSE

M. A. R. LeBlanc, D. J. Griffiths, and H. G. Mattes

Appl. Phys. Lett. 11, 143 (1967); http://dx.doi.org/10.1063/1.1755071 (4 pages) | Cited 4 times

Online Publication Date: 30 November 2004

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A transient increase of the temperature of the surface of a type II superconductor cooled in a static magnetic field causes flux expulsion and enhances the final diamagnetic moment. It is argued that a net paramagnetic current is induced at the surface of the specimen during the initial cooling in a static magnetic field. Quenching of this surface current by a heat pulse permits flux expulsion.

ELASTIC, PIEZOELECTRIC, AND DIELECTRIC PROPERTIES OF LITHIUM TANTALATE

R. T. Smith

Appl. Phys. Lett. 11, 146 (1967); http://dx.doi.org/10.1063/1.1755072 (3 pages) | Cited 10 times

Online Publication Date: 30 November 2004

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Room‐temperature values for all six independent elastic coefficients (at constant electric field) and all four independent piezoelectric stress coefficients have been determined from ultrasonic velocity measurements on a single‐crystal specimen of lithium tantalate grown by the Czochralski technique. The two independent dielectric constants at constant strain were derived from low‐frequency measurements on thin plates of lithium tantalate, in conjunction with the relevant elastic and piezoelectric data. The numerical results have been used to map the deviation of the elastic energy flux vector from the wave propagation direction for plane elastic wave propagation in the YZ crystallographic plane.

RADIAL DENSITY PROFILE AND CRITICAL MAGNETIC FIELD MEASUREMENT FOR THE HELICAL INSTABILITY IN A HOLLOW PLASMA COLUMN

J. F. Reynolds, E. H. Holt, W. C. Jennings, and J. H. Noon

Appl. Phys. Lett. 11, 148 (1967); http://dx.doi.org/10.1063/1.1755073 (3 pages) | Cited 2 times

Online Publication Date: 30 November 2004

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The characteristics of the current convective instability in a hollow plasma column are described. Langmuir probe measurements of the radial form of the perturbed electron density reveal that the rotating helix is concentrated towards the outer wall of the discharge vessel. The instability has been shown to occur at a lower critical magnetic field for a hollow plasma cell than for a regular positive column cell of the same dimensions. Neither of these features are considered in previous theoretical work. For both the regular and the hollow positive column, the use of measured electron density profiles in numerically evaluating a stability criterion is shown to give improved agreement between theory and experiment.

ZEEMAN EFFECT STUDIES OF THE WATER‐VAPOR LASER OSCILLATING ON THE 118.65 μm TRANSITION

W. J. Tomlinson, M. A. Pollack, and R. L. Fork

Appl. Phys. Lett. 11, 150 (1967); http://dx.doi.org/10.1063/1.1755074 (4 pages) | Cited 9 times

Online Publication Date: 30 November 2004

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Zeeman effect studies of the 118.65 μm line of a CW water‐vapor laser have shown that the levels involved in the transition have lifetimes between 0.04 and 0.4 μsec and the same total angular momentum, and that the transition has an effective magnetic moment of about 3∕4 of a nuclear magneton. These results were obtained by a new spectroscopic technique making explicit use of the saturation behavior of the laser oscillator. This technique enables lifetimes, angular momenta, and magnetic moments to be determined with magnetic field splittings of the order of or less than a tenth of the natural width of the transition.

SOLID‐STATE ACOUSTOELECTRIC LIGHT SCANNER

Basil W. Hakki

Appl. Phys. Lett. 11, 153 (1967); http://dx.doi.org/10.1063/1.1755075 (3 pages) | Cited 3 times

Online Publication Date: 30 November 2004

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Light‐emitting p‐n junctions are scanned by an acoustic domain traveling at sound velocity in CdS at room temperature. The light elements are heterojunctions formed by depositing p‐Cu2S on n‐CdS. The acoustic domain is generated in CdS by applying a bias electric field which gives the electrons a drift velocity greater than the shear sound velocity. When the acoustic domain is in the vicinity of a p‐n junction, part of the acoustic energy is transformed into light. As the domain travels between consecutive light elements it replenishes its lost acoustic energy from the bias electric field.

SCATTERING OF LIGHT BY ULTRASONIC SURFACE WAVES IN QUARTZ

J. Krokstad and L. O. Svaasand

Appl. Phys. Lett. 11, 155 (1967); http://dx.doi.org/10.1063/1.1755076 (3 pages) | Cited 6 times

Online Publication Date: 30 November 2004

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Experimental results of Raman‐Nath scattering of light by ultrasonic surface and volume waves in quartz are presented. The experiments indicate that the presented method will be a valuable tool for studying the effect of discontinuities upon surface wave propagation. It also appears that the phase velocity of the sound waves may be determined with good accuracy.

ULTRASONIC ATTENUATION IN SUPERCONDUCTING TIN AT VARIOUS AMPLITUDES OF THE ULTRASONIC PULSE

K. D. Chaudhuri and M. C. Jain

Appl. Phys. Lett. 11, 157 (1967); http://dx.doi.org/10.1063/1.1755077 (2 pages) | Cited 2 times

Online Publication Date: 30 November 2004

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The effect of amplitude of the ultrasonic pulse on the attenuation of pure and impure single crystals of superconducting tin has been studied for the strained as well as annealed specimens. It has been found that small amplitude favors oscillations and the temperature‐dependent attenuation is strongly dependent on the strain content of the specimen and slightly on amplitude.

TEMPERATURE DEPENDENCE AND MODEL OF THE ELECTRO‐OPTIC EFFECT IN LiNbO3

J. D. Zook, D. Chen, and G. N. Otto

Appl. Phys. Lett. 11, 159 (1967); http://dx.doi.org/10.1063/1.1755078 (3 pages) | Cited 44 times

Online Publication Date: 30 November 2004

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The temperature dependence and the absolute sign of the electro‐optic coefficients in single‐crystal LiNbO3 were measured in the temperature range of 20°‐250°C using a vibrating‐mirror Michelson interferometer. The linear electro‐optic effect in LiNbO3 is related through a simple model to the quadratic electro‐optic effect in paraelectric perovskites. The measured magnitude, sign, and the temperature dependence of the electro‐optic effect in this crystal are consistent with this model.

A NEW AND STABLE NONLINEAR OPTICAL MATERIAL

L. G. Van Uitert, S. Singh, H. J. Levinstein, J. E. Geusic, and W. A. Bonner

Appl. Phys. Lett. 11, 161 (1967); http://dx.doi.org/10.1063/1.1755079 (3 pages) | Cited 50 times

Online Publication Date: 30 November 2004

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The nonlinear coefficient d31 of K.6Li.4NbO3 is equal to d31 of LiNbO3. Also, the serious problem of optically induced refractive‐index inhomogeneities which has been observed in many nonlinear materials, notably LiNbO3, is not observed in this new material. The electro‐optic half‐wave voltage of this new material is 930 V.

A NEW METHOD FOR POINT TUNNELING INTO SUPERCONDUCTORS

S. von Molnar, W. A. Thompson, and A. S. Edelstein

Appl. Phys. Lett. 11, 163 (1967); http://dx.doi.org/10.1063/1.1755080 (2 pages) | Cited 11 times

Online Publication Date: 30 November 2004

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A novel point tunneling technique for superconductors is reported. This technique employs the intrinsic barrier layer formed between a degenerate GaAs point and the superconducting metal surface. Excellent agreement between theoretical and experimental conductance curves is obtained for polycrystalline lead.

ATMOSPHERIC ABSORPTION OF CO2 LASER RADIATION

John C. Stephenson, William A. Haseltine, and C. Bradley Moore

Appl. Phys. Lett. 11, 164 (1967); http://dx.doi.org/10.1063/1.1755081 (3 pages) | Cited 6 times

Online Publication Date: 30 November 2004

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See Also: Erratum

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The absorption of CO2 laser radiation by the atmosphere is calculated from laboratory absorption coefficient measurements.

REFLECTIVITY OF YIG AND YGG: OBSERVATION OF CHARGE TRANSFER AND CRYSTAL FIELD TRANSITIONS

Paul M. Grant

Appl. Phys. Lett. 11, 166 (1967); http://dx.doi.org/10.1063/1.1755082 (3 pages) | Cited 16 times

Online Publication Date: 30 November 2004

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The reflectivity spectra of yttrium iron garnet (YIG, Y3Fe5O12) and yttrium gallium garnet (YGG, Y3Ga5O12) have been measured in the energy range 2–7.5 eV. Structure is observed in YIG which can be attributed to charge‐transfer‐enhanced crystal field transitions and in YGG to critical point transitions.

STUDIES OF SUPERCONDUCTING Nb‐25% Zr WIRES CARRYING ALTERNATING CURRENT IN AN AXIALLY APPLIED MAGNETIC FIELD

Henry F. Taylor

Appl. Phys. Lett. 11, 169 (1967); http://dx.doi.org/10.1063/1.1755083 (3 pages) | Cited 13 times

Online Publication Date: 30 November 2004

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The application of an axially directed magnetic field has been observed to reduce ac losses considerably in superconducting Nb‐25% Zr wires. It has been found that magnetization curves measured with constant‐amplitude ac flowing in a wire sample are paramagnetic‐shifted with respect to curves measured with no externally supplied current. The presence of an axially applied field has been observed to increase the ac critical current with a maximum at about 2☒ kG applied field.

PREPARATION AND PROPERTIES OF HIGH‐PURITY EPITAXIAL GaAs GROWN FROM Ga SOLUTION

C. S. Kang and P. E. Greene

Appl. Phys. Lett. 11, 171 (1967); http://dx.doi.org/10.1063/1.1755084 (3 pages) | Cited 14 times

Online Publication Date: 30 November 2004

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GaAs single crystals were grown epitaxially from Ga solution with carrier concentrations in the 1014 cm‐3 range and electron mobilities between 7500 and 9300 cm2∕V‐sec at 300°K, and 50,000 and 95,000 cm2∕V‐sec at 77°K. A comparison of the theoretical and experimental curves for the mobility vs temperature indicates that the significant scattering mechanisms are ionized impurities and phonons in the temperature range of 77°K to 430°K. This indicates that the epitaxial layers do not contain other mobility‐limiting imperfections to a significant degree. Photoluminescence spectra of the epitaxial layers did not show any emission due to keep lying imperfection levels.
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