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1 Oct 1960

Volume 31, Issue 10, pp. 1699-1848

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Domains in Thin Magnetic Films Observed by Electron Microscopy

Harrison W. Fuller and Murray E. Hale

J. Appl. Phys. 31, 1699 (1960); http://dx.doi.org/10.1063/1.1735428 (7 pages) | Cited 39 times

Online Publication Date: 16 June 2004

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A new method for observing full domains in thin magnetic films by electron microscopy is described. Observations are made with standard transmission instruments utilizing an off‐centered objective aperture diaphragm as a knife edge. The method has the high‐resolution advantage that the microscope is focused on the specimen during domain observations. Limitations of the method and comparisons with the previously reported defocusing technique are presented. Applications to the interpretation of complex domain patterns and cross‐tie walls are demonstrated. The observations were made with electrostatic‐focusing microscopes, the AEG‐Zeiss and Trüb‐Täuber instruments, which allow the use of full objective power without influencing the magnetization distribution of low coercive force films. A second method using a knife edge is proposed that would potentially permit a simple measurement of the detailed magnetization distribution of a domain wall in a thin film.

Longitudinal Wave Propagation in Stretched Polymers

Peter Mason

J. Appl. Phys. 31, 1706 (1960); http://dx.doi.org/10.1063/1.1735429 (3 pages) | Cited 5 times

Online Publication Date: 16 June 2004

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The wave equation is derived for the propagation of longitudinal waves along a stretched filament of a highly elastic material. It is found that the tension in the filament reduces the effective modulus by twice the product of Poisson's ratio and the tensile traction, leaving the internal viscosity term unchanged. This result is illustrated by measurements of continuous 1 kcps wave propagation in natural rubber at 50°C, where the damping is small (tan δ<0.1). An alternative derivation is given for the purely elastic case of zero damping without restriction upon the amplitude.
The ``equilibrium'' or ``static'' Young's modulus is obtained for extensions up to about 600% from the slope of the equilibrium stress‐strain curve and used to predict the corresponding wave velocities from the wave equation for zero damping. The predicted velocities are slightly higher—by up to about 10%—than the measured velocities. It is shown that the deviations could arise from differences in rate of strain between the wave‐propagation and the stress‐strain measurements. At the higher extensions the rubber is very hysteretic for large deformations, and the Young's modulus governing the small‐amplitude wave propagation is shown to relate substantially to the loading branch of the stress‐strain curve.

Cathode of an Arc in Xenon

John E. White

J. Appl. Phys. 31, 1709 (1960); http://dx.doi.org/10.1063/1.1735430 (6 pages) | Cited 2 times

Online Publication Date: 16 June 2004

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Energy balance, space charge, and thermionic equations have been combined to provide a description of the mechanism of the cathode in an ac arc, and the quantities required for solution determined experimentally. The experiments were carried out on barium‐activated electrodes in xenon at 1.4 atm and extended over a range of 25–75 amps rms. The work function was found to be 1.77 v at zero‐field and reduced to 1.67 v under Schottky effect of the space charge field. The work function did not change with current, but the Richardson‐Dushman A fell, as the current was raised, to a value of approximately 0.1 at the highest load. The cathode fall varied with phase angle and showed a maximum of 1.2 v at maximum current. The component of current at the cathode carried by ions reduced from 12% to 6% as the load increased.

Density of a Thorium Monolayer for Maximum Thermionic Emission

W. E. Danforth and D. L. Goldwater

J. Appl. Phys. 31, 1715 (1960); http://dx.doi.org/10.1063/1.1735431 (3 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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An investigation is described in which a high‐sensitivity analytical balance of standard design is used for determination of the surface density of that thorium layer which corresponds to maximum thermionic emission with the thorium‐on‐tungsten system. Following Brattain and Becker's definition of this value of surface density as one ``f unit,'' thorium vapor is allowed to accumulate on a quartz plate until a weighable number of f units (about 600) has been deposited. The thorium flux in f units per minute is monitored periodically by means of a tungsten filament diode during the course of the deposition. Two polycrystalline specimens of ribbon from the same source have yielded the value of (4.2±0.2)1014 atoms∕cm2 as the density for maximum emission. This is to be compared with a value of 5.0×1014 atoms∕cm2 obtained in 1934 on theoretical grounds by Langmuir.

Anomalous Barrier Capacitance in p‐n Junctions of InSb

C. A. Lee and G. Kaminsky

J. Appl. Phys. 31, 1717 (1960); http://dx.doi.org/10.1063/1.1735432 (3 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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Reverse bias transition capacitance measurements on alloy diodes of InSb at 78°K give values a factor of three times those calculated from normal diode theory. This result is in contrast to the reasonable agreement obtained for diodes of germanium and gallium arsenide in a comparable doping range. The experimental techniques are critically reviewed and an attempt made to assess the implications of the results.

Growth of Cesium Chloride Crystals from Solution and Melt

P. Avakian and A. Smakula

J. Appl. Phys. 31, 1720 (1960); http://dx.doi.org/10.1063/1.1735433 (3 pages) | Cited 13 times

Online Publication Date: 16 June 2004

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Large cesium chloride crystals were obtained from solution only upon addition of urea. These crystals, however, show NH4+ impurity. Since CsCl undergoes a phase transition between its melting point and room temperature, normal growing methods from the melt could not be used, but a modified (``double‐run'') Bridgman method yielded good results.

Propagation Constants for Electromagnetic Waves in Weakly Ionized, Dry Air

A. V. Phelps

J. Appl. Phys. 31, 1723 (1960); http://dx.doi.org/10.1063/1.1735434 (7 pages) | Cited 30 times

Online Publication Date: 16 June 2004

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Formulas and graphs are given for the calculation of the propagation constants of an electromagnetic wave in weakly ionized, dry air at ionospheric temperatures in the presence of a magnetic field. Experimental studies of electron collision frequencies in nitrogen and oxygen are reviewed and used to obtain the magnitude and energy dependence of the electron collision frequency in air. The equations for the components of the conductivity tensor are developed taking into account the approximately linear dependence of the electron collision frequency on electron energy. Expressions derived on this assumption are found to be accurate except at low temperatures, high pressures, and low frequencies. The errors resulting from the use of an effective value for the energy independent collision frequency in the Appleton‐Hartree equations are evaluated. Procedures are given for the calculation of the propagation constants for electromagnetic waves propagated parallel to and perpendicular to the magnetic field. These results are then applied to the derivation of relations required to reanalyze the ionospheric collision frequency measurements reported by Kane. The use of an effective collision frequency is found to lead to errors comparable to the experimental errors in the ionospheric observations.

Effects of Internal Oxidation and Heat Treatment on the Electrical Resistivity of Dilute CuMn, CuFe, and CuCo Alloys

C. A. Domenicali and E. L. Christenson

J. Appl. Phys. 31, 1730 (1960); http://dx.doi.org/10.1063/1.1735435 (4 pages) | Cited 7 times

Online Publication Date: 16 June 2004

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This investigation was concerned with the effects of high temperature treatment in vacuo or in rarefied oxygen atmospheres upon the effective electrical resistivity of dilute (copper‐rich) CuMn, CuFe, and CuCo rods and wires. The CuMn alloys studied most extensively contained between 1 and 12 at. % manganese while the CuFe and CuCo alloys contained between 0.1 and 0.3 at. % iron or cobalt. It was found that the solutes in the CuFe and CuCo wires and rods become rapidly oxidized (internally) during heat treatment for several hours at 990°C in pure oxygen pressures of 0.5 μ or greater, while in 0.05 μ O2 this oxidation is absent and previously oxidized specimens are reduced. These observations are based on measurements of electrical resistivity, and in the case of CuFe, substantiated by measurements on the magnetization. Heat treatment of these CuFe and CuCo wires and rods near 1000°C for several hours either in vacuo (0.1 μ air) or 5 μ O2 does not appreciably affect the cross‐sectional uniformity of these specimens. In the case of CuFe alloys, the magnetic behavior demonstrates the virtually complete oxidation of solute to Fe3O4 after prolonged anneal in an oxidizing atmosphere. The behavior of the CuMn alloys was found to be more complicated, partly because of the high solute concentrations involved. It was found that wires and rods of CuMn rapidly become nonuniform in solute concentration throughout their cross section when annealed near 1000°C for several hours either in a vacuum (0.1 μ air) or in 5 μ of pure oxygen; this nonuniformity of manganese concentration develops at a considerably higher rate in the 5 μ O2 atmosphere than in vacuum, and leads to erroneous values of the resistivity and to erroneous curves of resistivity vs temperature for CuMn wires or rods. On the other hand, annealing of such wires for several hours in vacuum at temperatures around 800°C does not appreciably disturb the cross‐sectional uniformity. Finally, it is emphasized that the ``carrier gas'' technique (involving a flow system with small concentrations of oxygen mixed with helium at atmospheric pressure, for example) is entirely unsatisfactory for experiments on internal oxidation, particularly if one wants to know the oxygen partial pressure.

An Improved Method of Growing CdS Crystals from the Vapor Phase

P. D. Fochs

J. Appl. Phys. 31, 1733 (1960); http://dx.doi.org/10.1063/1.1735436 (2 pages) | Cited 17 times

Online Publication Date: 16 June 2004

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The gradual increase in the difference in temperatures of two Kanthal heating elements enables CdS crystals to be grown directly on the inside of a silica tube, remote from one another, instead of on a continuous polycrystalline CdS substrate as happens in most existing methods.

Note on Evaporation

S. A. Zwick

J. Appl. Phys. 31, 1735 (1960); http://dx.doi.org/10.1063/1.1735437 (7 pages) | Cited 3 times

Online Publication Date: 16 June 2004

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A simple kinetic model is employed to investigate nonequilibrium evaporation from a liquid. Molecules are assumed to evaporate into a (one‐sided) Maxwellian velocity distribution at the liquid surface. Molecules reaching the surface from the vapor are assumed to form part of an ellipsoidal velocity distribution. Of the molecules approaching the liquid at the interface only the fraction α condenses there; the remainder is taken to undergo specular reflection back into the vapor. By equating physical conditions at the surface with conditions in the vapor, one can relate the vapor pressure to that which would prevail at equilibrium, as a function of the surface accommodation coefficient α and the mean velocity u of the vapor relative to the interface.

Aperture Fields in the Diffraction by a Slit

Hwei‐Piao Hsu

J. Appl. Phys. 31, 1742 (1960); http://dx.doi.org/10.1063/1.1735438 (5 pages) | Cited 2 times

Online Publication Date: 16 June 2004

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Aperture fields in the diffraction by a slit was studied numerically and experimentally. Numerical calculations are based on the exact solution in the form of an infinite series of Mathieu functions. Experimental measurements, by means of a parallel‐plate device, of the field distribution over the aperture in slits of 3.5λ, 3λ, 2.21λ, 1.27λ width (λ=wavelength) are discussed, and show satisfactory agreement with the exact solution for slits of width 1.27λ and 2.21λ. The exact solution of diffraction by a slit due to a line source is also presented in the Appendix.

Grain‐Boundary Photoresponse

W. W. Lindemann and R. K. Mueller

J. Appl. Phys. 31, 1746 (1960); http://dx.doi.org/10.1063/1.1735439 (6 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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Measurements of the sensitivity of grain‐boundary photodetectors indicate an expected minimum detectable power of better than 10−14 w. Major factors governing the sensitivity are the minority carrier lifetime and the distance of the boundary from the irradiated surface. Spectral measurements show an added absorption edge response at about 1.67 μ and 1.72 μ. This added response could be caused by deep‐lying acceptor levels or by excitons with a long lifetime. However, the experimental evidence points to direct absorption at the grain boundary as the most likely reason for the absorption edge irregularities.

Surface Space‐Charge Calculations for Semiconductors

D. R. Frankl

J. Appl. Phys. 31, 1752 (1960); http://dx.doi.org/10.1063/1.1735440 (3 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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Approximation formulas for the surface excesses of carriers at large values of the reduced surface and bulk potentials are derived, and computed results are presented.

Oblique‐Incidence Anisotropy in Evaporated Permalloy Films

D. O. Smith, M. S. Cohen, and G. P. Weiss

J. Appl. Phys. 31, 1755 (1960); http://dx.doi.org/10.1063/1.1735441 (8 pages) | Cited 129 times

Online Publication Date: 16 June 2004

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Magnetic anisotropy has been observed in evaporated Permalloy films deposited at oblique incidence of the vapor. Electron micrographs of such films reveal chains of crystallites whose long axes are oriented perpendicular to the vapor beam. A ``self‐shadowing'' model is proposed to explain chain growth, i.e., the area behind a crystallite is left vacant because it is in the crystallite's shadow. Oriented crystallite chains are thus caused by a purely geometric process; their existence has also been demonstrated for Au, Pt, W, and Mg. Oriented chains give rise to a number of macroscopic effects: magnetic anisotropy, anisotropic resistance, dichroism, and anisotropic resonance linewidth. Experiments involving the stripping of oblique‐incidence Permalloy films from their substrates indicate the presence of an anisotropic strain which, in conjunction with magnetostriction, gives another contribution to the magnetic anisotropy; this contribution explains the observed compositional dependence of the magnetic anisotropy. Surface tension, which tends to contract the crystallite chains, is postulated as the generating force of anisotropic strain; surface tension could similarly generate the isotropic strain which is found in normal‐incidence films.

Ordering in the Intermediate Phases TiFe, TiCo, and TiNi

Paul Pietrokowsky and Frank G. Youngkin

J. Appl. Phys. 31, 1763 (1960); http://dx.doi.org/10.1063/1.1735442 (4 pages) | Cited 14 times

Online Publication Date: 16 June 2004

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The intermediate phases TiFe, TiCo, and TiNi have been investigated by x‐ray powder diffraction techniques. The atomic arrangements of these ensembles have been determined to be of the cesium chloride, B2 type. Monochromatic x radiation was utilized in the investigation.

On a Complex Recrystallization Texture in 3% Silicon Iron

C. G. Dunn and C. J. McHargue

J. Appl. Phys. 31, 1767 (1960); http://dx.doi.org/10.1063/1.1735443 (4 pages)

Online Publication Date: 16 June 2004

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Components in a complex primary recrystallization texture, which is a matrix texture for secondary recrystallization to the Goss texture in 3% silicon‐iron strip, have been determined by the axis‐chart method of Jetter, McHargue, and Williams. The results obtained are compared with former pole‐figure results and found to include components not previously resolved or noted. It is found also that the components of the texture explain reasonably well the observed magnetic torque curve of the material.

Hall Field Relaxation in Semiconductors at High Frequency

Keith S. Champlin

J. Appl. Phys. 31, 1770 (1960); http://dx.doi.org/10.1063/1.1735444 (2 pages)

Online Publication Date: 16 June 2004

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Using a simple extension of standard magneto‐ionic theory, the frequency dependence of the complex Hall field is calculated for samples with rectangular, cylindrical, and spherical geometry. The result has application to ``open‐circuit'' Hall effect measurements on semiconductors at microwave frequencies.

Fast Neutron Bombardment of Germanium and Silicon Esaki Diodes

J. W. Easley and R. R. Blair

J. Appl. Phys. 31, 1772 (1960); http://dx.doi.org/10.1063/1.1735445 (3 pages) | Cited 6 times

Online Publication Date: 16 June 2004

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The fast neutron irradiation behavior of germanium and silicon Esaki diodes has been experimentally examined. The dominant change produced is an increase in the ``excess'' current which is proportional to integrated neutron flux. The observed increase in the vicinity of the current minimum is approximately 2.6×10−15 amp∕fast neutron and 1.1×10−14 amp∕fast neutron for germanium and silicon diodes respectively. Substantial changes result in the voltage‐current characteristics of the diodes employed in the decade of exposure between 1016–1017 fast neutrons∕cm2 for germanium diodes and between 1015–1016 fast neutrons∕cm2 for silicon diodes. One kilomegacycle cavity oscillators employing germanium diodes exhibit a marked reduction in power output in the decade of exposure between 1016–1017 fast neutrons∕cm2. The magnitude of the decrease is in approximate agreement with the observed bombardment reduction of diode negative conductance.

Interaction between High‐Power Microwave Losses and Magnetic Flux Reversal

E. M. Gyorgy and F. B. Hagedorn

J. Appl. Phys. 31, 1775 (1960); http://dx.doi.org/10.1063/1.1735446 (4 pages) | Cited 5 times

Online Publication Date: 16 June 2004

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The off‐resonance microwave absorption (subsidiary absorption) which frequently occurs at high‐microwave power and which may exist even in the absence of an external dc magnetic field has been used to observe the interaction between the magnetic flux reversal and the microwave loss processes in polycrystalline ferrite. These experiments have shown that the spin waves associated with high‐power, off‐resonance microwave absorption have a negligible effect on the flux reversal process. However, the flux reversal process has a marked effect on the high‐power microwave loss. During the flux reversal process, this high‐power, off‐resonance microwave absorption was found in some cases to be negligible.

On the Strength of Glass in Water Vapor

F. R. L. Schoening

J. Appl. Phys. 31, 1779 (1960); http://dx.doi.org/10.1063/1.1735447 (6 pages) | Cited 6 times

Online Publication Date: 16 June 2004

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The bending strength of glass slides, which had the dimensions 38×6×0.16 mm, was measured at different relative pressures of water vapor. The adsorption isotherms of water vapor on powdered glass, which had the same composition as the slides, were measured in a separate experiment. The reduction of the surface free energy as function of the vapor pressure was calculated from the isotherms. The observed variation of the strength was compared with the strength variation calculated from the reduction of the surface free energy. The Griffith equation for brittle fracture was used to relate strength and surface free energy. Two cases were considered: (1) the specimens were weakened by the reduction of the surface free energy and (2) the specimens were weakened by the reduction of the surface free energy and by a deepening of the surface cracks. Both interpretations agreed with the experimental results because, by using the Griffith equation, only the lower limits for the strength of the specimens could be calculated.
It was found that the observed strength did not decrease steadily with increasing vapor pressure, but had a secondary maximum at a relative pressure of about 0.2. The maximum reduction of the strength corresponding to complete wetting with water was already reached at a relative pressure of about 0.5. The ratio of the strength in saturated water vapor to the strength in vacuum was found to be independent of the surface damage of the specimens.

Study of Irradiation Effects and the H2+H2 Buildup in Tantalum

A. F. Gabrysh, H. Eyring, M. E. Wadsworth, G. S. Baker, and T. Ree

J. Appl. Phys. 31, 1785 (1960); http://dx.doi.org/10.1063/1.1735448 (7 pages)

Online Publication Date: 16 June 2004

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The irradiation effects and the increase of neutron yield from the deuterium‐deuterium reaction in tantalum has been studied at a bombarding energy of 350 kev and a target current 100 μa. Saturation (the neutron yield becomes a steady maximum) is reached in a new target, maintained at temperatures below 45°C, after about 2 hours of steady bombardment or on the order of 1 coulomb of deuterons per square centimeter. The irradiated targets were annealed at temperatures from 45°C to 770°C. A thermal analysis shows that a prominent exothermic maximum in the annealing spectrum occurs at approximately 612°C. This maximum is associated with an increase in pressure, indicating an abrupt increase in diffusion of deuterium from the target at this temperature. From a study of diffusion of deuterium from the specimen at three temperatures, an activation energy of 0.24 ev is calculated for diffusion of deuterium in tantalum.
X‐ray traces were taken of the specimen before and after bombardment and after annealing. These showed an expansion of the lattice together with changes in line intensities indicating a distortion in the lattice structure.

Anomalous Surface Channels on Silicon p‐n Junctions

Raymond Solomon

J. Appl. Phys. 31, 1791 (1960); http://dx.doi.org/10.1063/1.1735449 (9 pages) | Cited 1 time

Online Publication Date: 16 June 2004

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A chopped‐light spot has been used to explore the photoresponse of silicon p‐n junction surfaces. Anomalous channel responses extending in some cases to distances of 100 mils or more, have been observed on accumulation layer and intrinsic barrier surfaces. The phase shift of the induced ac photocurrent is measured as a function of the distance of the light spot from the junction, and phase shifts of more than 380° have been observed for the anomalous channels. Experimental evidence is offered to show that the excessive phase shift is due to multiple trapping of the injected carriers at surface interface states. Additional evidence indicates that the anomalous channels are a result of an interaction of the fringing field with the slow surface states.

Effect of Thermal History on the Dislocation Substructure near the Surfaces of a Lithium Fluoride Crystal

J. M. Schultz and J. Washburn

J. Appl. Phys. 31, 1800 (1960); http://dx.doi.org/10.1063/1.1735450 (2 pages) | Cited 4 times

Online Publication Date: 16 June 2004

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A series of x ray and etch pit experiments has been performed to determine some of the effects of temperature on the perfection of surface layers in LiF. It was found that the perfection of a cleaved surface is substantially increased at temperatures near the melting point, that rearrangement and annihilation of dislocations takes place at much lower temperatures, and that rapid cooling promotes the formation of shallow dislocation loops.

Anisotropy of the Magnetic Susceptibility of Gallium

Titus Pankey

J. Appl. Phys. 31, 1802 (1960); http://dx.doi.org/10.1063/1.1735451 (3 pages) | Cited 5 times

Online Publication Date: 16 June 2004

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The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25°C. The following anisotropic diamagnetic susceptibilities were found: a axis (−0.119±0.001)×10−6 emu∕g, b axis (−0.416±0.002)×10−6 emu∕g, and c axis (−0.229±0.001) emu∕g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (−0.257±0.003)×10−6 emu∕g at 25°C, and (−0.299±0.003)×10−6 emu∕g at −196°C. The susceptibility of liquid gallium was (0.0031±0.001)×10−6 emu∕g at 30°C and 100°C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi‐energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state.

Measurements of the Dielectric Constant of BaTiO3 Single Crystals in the Paraelectric Region at X Band

A. Lurio and E. Stern

J. Appl. Phys. 31, 1805 (1960); http://dx.doi.org/10.1063/1.1735452 (5 pages) | Cited 12 times

Online Publication Date: 16 June 2004

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The dielectric constant and loss tangent of single crystals of BaTiO3 were measured as a function of temperature in the frequency range of 8.2 to 12.4 kMc. The technique consisted of looking for transmission resonances through the crystal whenever its thickness became λ∕2 (where λ is the wavelength in the material). From the Curie‐Weiss behavior of the dielectric constant in the paraelectric region, the A constant was determined to be 3.77×10−5°C−1.
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