# Showing papers in "Journal of Applied Physics in 1966"

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TL;DR: In this article, it is shown that coalescence of steps or stabilization of step spacings can occur as a consequence of assuming that capture probabilities are directionally dependent, and a general solution for the time-dependent step distribution is obtained in terms of these probabilities and an arbitrary initial distribution of an infinite sequence of parallel steps.

Abstract: It is postulated that steps on crystal surfaces capture atoms diffusing on the surface with certain probabilities and, in addition, that the capture probability depends on the direction from which adsorbed atoms approach the step. A general solution for the time‐dependent step distribution is obtained in terms of these probabilities and an arbitrary initial distribution of an infinite sequence of parallel steps. It is shown that coalescence of steps or stabilization of step spacings can occur as a consequence of assuming that capture probabilities are directionally dependent. Some of the implications of the theoretical model are related to the growth of real crystal surfaces.

1,367 citations

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TL;DR: In this article, the fundamental optical absorption edge of indium oxide at room temperature was investigated, and it was shown that the minimum of the conduction band is at k=0 and the maximum of the valence band was at k≠0.

Abstract: In an investigation of the fundamental optical absorption edge of indium oxide at room temperature, transitions identified as direct‐allowed have been observed with an energy gap (probably at k=0) of 3.75 eV. Indirect‐forbidden transitions have also been observed with an energy gap of 2.619 eV and an assisting phonon of 0.069 eV. It is proposed that the minimum of the conduction band is at k=0 and the maximum of the valence band is at k≠0.

424 citations

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TL;DR: In this article, an experimental determination of the magnitude of this stress and its dependence on the temperature of oxidation was made by two techniques: (a) the thin Si sample was used as a beam, and the amount of bowing under the strain exerted by oxide left on one surface was measured; (b) the unsupported SiO2 window was used by a balloon, and strain was measured as a function of air pressure inflating the balloon.

Abstract: When Si is thermally oxidized, the SiO2 resulting is in a state of compression on the surface This paper reports an experimental determination of the magnitude of this stress and its dependence on the temperature of oxidationSamples of (111)‐ and (100)‐oriented Si were oxidized at several temperatures between 875°–1200°C to thicknesses of 2000 A‐20 000 A Stress determination was made by two techniques: (a) the thin Si sample was used as a beam, and the amount of bowing under the strain exerted by oxide left on one surface was measured; (b) the unsupported SiO2 window was used as a balloon, and strain was measured as a function of air pressure inflating the balloon Results of these measurements are in agreement with the stress expected from thermal mismatch of Si and SiO2 For an oxidation carried out at 1200°C the measured stress is 31×109 dyn/cm2 The data from the SiO2 balloons showed that the strain grown in the oxide was greater than 10−3 In addition, determination was made of Young's modulus fr

380 citations

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TL;DR: In this article, Ferroelectricity and weak ferromagnetism have been found to set on simultaneously in Ni3B7O13I at about 64°K.

Abstract: Ferroelectricity and weak ferromagnetism have been found to set on simultaneously in Ni3B7O13I at about 64°K. This is evidenced by dielectric hysteresis, spontaneous Faraday effect, quadratic magnetoelectric hysteresis, etc. The strong coupling between the mutually perpendicular spontaneous polarization—[001]—and spontaneous magnetization—[110]—is such that, when the former is reversed, the latter turns by 90°. The magnetic point group is most probably m′m2′. Dielectric constant, magnetic, and magnetoelectric susceptibilities and magnetic coercive field are shown as a function of temperature.

352 citations

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309 citations

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TL;DR: In this paper, the saturation effect in the stimulated Brillouin scattering of coherent light waves was analyzed and two coupled first-order nonlinear equations for the intensities of the primary and Stokes waves were proposed.

Abstract: An analysis is given of the saturation effect in the stimulated Brillouin scattering of coherent light waves. It is shown that the three coupled nonlinear wave equations describing the complex amplitudes of the forward‐traveling primary and acoustic waves and the backward‐traveling Stokes wave can be replaced for room‐temperature situations by two coupled first‐order nonlinear equations for the intensities of the primary and Stokes waves. These resulting equations are solved exactly and the solutions describe completely the process of photoelastic amplification of the coherent Stokes wave via stimulated Brillouin scattering in both the linear and the nonlinear saturated regimes. The results also give a more realistic estimate of the intensity of the hypersonic wave generated in the process than that made on the basis of either the Manley‐Rowe relationship, which does not take into account the losses, or the usual linear theories, which do not take into account the saturation effect. It is believed that th...

294 citations

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TL;DR: In this paper, the adiabatic elastic constants c44, ½(c11−c12), and ½ (c11+c12+2c44) have been measured for copper, silver, and gold over the temperature range from 300° to about 800°K using the conventional ultrasonic pulse-echo technique.

Abstract: The adiabatic elastic constants c44, ½(c11−c12), and ½(c11+c12+2c44) have been measured for copper, silver, and gold over the temperature range from 300° to about 800°K using the conventional ultrasonic pulse‐echo technique. The room‐temperature values of the stiffness coefficients are shown to be in acceptable agreement with previously published data for the noble metals. Over the entire range from 300° to 800°K, it is found that, to a remarkably good approximation, the elastic constants for all three metals decrease linearly with temperature. Additional evidence is presented to show that the linear temperature dependence of the elastic constants for silver extends to at least 1000°K, i.e., to within 80% of the absolute melting temperature. The isothermal compressibilities calculated from the elastic constant data are used to evaluate the dilational term in the specific heat, Cdil=Cp−Cv, and it is established that the approximate Nernst‐Lindemann relation for estimating Cdil is valid for Cu, Ag, and Au a...

268 citations

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TL;DR: In this paper, an energy-level diagram has been proposed to account for the optical and electrical properties as well as the color center formation in MoO3, and the growth and decay of color centers has been studied in detail.

Abstract: The optical absorption spectrum of thin films of MoO3 has been measured over the temperature range from 77° to 290°K. The fundamental absorption edge occurs at 3300 A with an absorption coefficient of 105 cm−1. A stoichiometric film of MoO3 shows three absorption peaks at 3350, 2880, and 2700 A, respectively, and these are suggested to be due either to exciton formation or to transitions involving a split valence band.Values for the refractive index have been measured in the wavelength range 0.42–1.2μ. The low‐frequency dielectric constant (18.0±1) has been measured and the comparison with the high‐frequency dielectric constant (5.70) indicates that the bonding is predominantly ionic.The electrical conductivity has been measured on a polycrystalline sample in the temperature range 298° to 900°K and the activation energies of conduction found to be 1.83 eV (intrinsic) and 0.56 eV (impurity).On irradiating a thin film (0.2μ) of MoO3 with light of wavelength shorter than 3300 A, three color‐center bands having maxima around 5000, 6250, and 7700 A are formed. The same type of color centers are also formed on heating the film in oxygen in inert atmosphere. The color centers thus formed cannot be bleached optically. However, they can be bleached thermally in oxygen at 300°C. The growth and decay of color centers has been studied in detail.The formation of color centers is associated with increased dark conductivity of the MoO3. Very weak photoconductivity and photovoltaic effects with threshold energy corresponding to the fundamental absorption edge at 3300 A have been observed.An ESR signal characteristic of Mo5+ state has been observed in a film of MoO3. There is a small increase of ESR signal on color‐center formation which disappears completely on heating in air at 300°C.An energy‐level diagram has been proposed to account for the optical and electrical properties as well as the color‐center formation in MoO3.

260 citations

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TL;DR: In this article, all 14 third-order elastic coefficients of quartz have been calculated from the measured transit times for small-amplitude ultrasonic waves as functions of applied stress.

Abstract: All 14 third‐order elastic coefficients of quartz have been calculated from the measured transit times for small‐amplitude ultrasonic waves as functions of applied stress. Thirty‐four different experimental runs were made, ten under hydrostatic pressure, and 24 under uniaxial stress. The data permit calculation of the 14 coefficients with 20 crosschecks. Our recommended values at 25°C, based on a least‐squares fit, are as follows, all in 1012 dyn/cm2. CoefficientValueStandard errorC111−2.100.07C112−3.450.06C113+0.120.06C114−1.630.05C123−2.940.05C124−0.150.04C133−3.120.07C134+0.020.04C144−1.340.07C155−2.000.08C222−3.320.08C333−8.150.18C344−1.100.07C444−2.76 0.17.

253 citations

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TL;DR: In this article, the authors used a vertical dc magnetic field to damp the thermal convection in the molten sample to suppress turbulence, thereby eliminating the temperature fluctuations in the liquid that cause the solute bands.

Abstract: Samples of tellurium‐doped indium antimonide that exhibited solute banding when solidified in a horizontal boat under ordinary conditions showed no bands when solidified in the presence of a vertical dc magnetic field. The effect of the field was to damp the thermal convection in the molten sample to the point of suppressing turbulence, thereby eliminating the temperature fluctuations in the liquid that cause the bands.

242 citations

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TL;DR: In this paper, a parametric criterion is developed from physical arguments, and it is used to interpret systematically the magnetic and electric properties of oxides with the perovskite structure.

Abstract: In many oxides the outer d electrons are not localized, magnetic electrons but collective, metallic electrons either as a result of cation‐sublattice band formation or of covalent mixing of anion p and cationic d states. It is shown that cation‐sublattice band formation does not take place in oxides with ReO3 or perovskite structure and that they are therefore suitable for testing any covalency criterion for the magnetic vs metallic state. A parametric criterion is developed from physical arguments, and it is used to interpret systematically the magnetic and electric properties of oxides with the perovskite structure. The role of the Hartree—Fock intra‐atomic exchange correlations is found to be important, and the physical origin of the ferroelectric transitions is identified.

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TL;DR: In this article, it was shown that a combined investigation of the magnetic and the semiconducting properties of the solid solutions of LaMnO3 and LaCoO3 is necessary for a complete understanding of this rather complicated system.

Abstract: In this paper it is shown that a combined investigation of the magnetic and the semiconducting properties of the solid solutions of LaMnO3 and LaCoO3 is necessary for a complete understanding of this rather complicated system. The conductivity gives information on the valency states of the ions and with this knowledge the magnetic properties become understandable. Mixtures of Mn3+ and Co3+ ions tend to the formation of Mn4+–Co2+ pairs having a positive magnetic superexchange interaction.

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TL;DR: In this article, it was shown that the total entropy change at the transition of FeRh is much larger than the estimated change in lattice entropy (ΔS)lat, which is attributed to thermal excitation of the Rh moments which in the ferromagnetic state are induced.

Abstract: Previous measurements of the critical temperature (Tcrit) for the first‐order antiferromagnetic‐ferromagnetic transition in FeRh as a function of magnetic field have established that the total entropy change at the transition (ΔS) is much larger than the estimated change in lattice entropy (ΔS)lat. This study has now been extended to pseudobinary variants of FeRh where the Rh is partially replaced by Pd, Pt, or Ir, resulting in a large decrease or increase of Tcrit from its value (about 330°K) for FeRh. In each case, a value for ΔS was deduced from the measured field dependence of Tcrit. The difference between each ΔS and an estimated (ΔS)lat value, when plotted vs Tcrit, defines a smooth curve with a maximum at about 500°K, which is just below the Curie points of these alloys. It is therefore concluded that ΔS−(ΔS)lat represents an entropy change of magnetic origin. This anomalous change in magnetic entropy is attributed to thermal excitation of the Rh moments which in the ferromagnetic state are induced...

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TL;DR: The elastic constants of zirconium carbide and titanium carbide were determined over the temperature range of 4.2° to 298°K using a pulsed-ultrasonic phase comparison technique, and are compared to previously determined values for uranium carbide as discussed by the authors.

Abstract: The elastic constants of zirconium carbide and titanium carbide were determined over the temperature range of 4.2° to 298°K using a pulsed‐ultrasonic phase comparison technique, and are compared to previously determined values for uranium carbide. Since these carbides are of the NaCl structure, only three independent constants are required to describe their elastic behavior. Their values at 298°K are ZrC0.94TiC0.91C114.720±0.0055.145±0.005C120.987±0.0051.060±0.002C441.593±0.0021.788±0.002 all in units of 1012 dyn/cm2. The differences in the elastic behavior of these group IV, transition metal carbides and the monocarbide of uranium are discussed in reference to their different electronic structure.

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TL;DR: In this article, a 20mm light-gas gun was used to accelerate a driver plate against a target at velocities up to 8 km/sec. Tests have been conducted using Fansteel 77 drivers, and Hugoniot data have been obtained for Fansteel, tungsten, and gold to about 6 mbar pressure.

Abstract: Equation‐of‐state data at extremely high pressure is required for the analysis of many problems pertaining to physics, geophysics, astrophysics, etc. The conventional method used to obtain such data is to impact one flat plate of material against another flat plate at a very high velocity. A shock wave is thus produced in the target plate and the pressure can be deduced by measuring the impact velocity and the shock velocity. American, Russian, and British researchers have used explosive to propel the driver plate to velocities of about 5 km/sec; however, the Russians do not indicate how they accelerate their driver plates for their highest velocities (14–15 km/sec).The present paper describes an experimental technique in which a 20‐mm light‐gas gun has been used to accelerate a driver plate against a target at velocities up to 8 km/sec. Tests have been conducted using Fansteel 77 drivers, and Hugoniot data have been obtained for Fansteel 77, tungsten, and gold to about 6‐Mbar pressure. The technique is v...

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TL;DR: In this paper, the dielectric and electro-optic properties of KTaxNb1−xO3 (KTN) are discussed from the point of view of the material's usefulness in light modulators and beam deflectors.

Abstract: The dielectric and electro‐optic properties of KTaxNb1−xO3(KTN) are discussed from the point of view of the material's usefulness in light modulators and beam deflectors. It is shown that baseband light modulators with 200‐ to 300‐Mc/sec bandwidths and analog deflectors with 200 to 300 resolvable spots are within the practical capabilities of this material.

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TL;DR: In this article, chemical, electrical, and optical measurements were performed on n and p-type β-silicon carbide crystals grown from pure or doped carbon-saturated silicon melts.

Abstract: Chemical, electrical, and optical measurements were performed on n‐ and p‐type β‐silicon carbide crystals grown from pure or doped carbon‐saturated silicon melts. Pure, transparent yellow crystals showed no detectable impurities and had carrier concentrations in the range of 1016 cm−3. Extensive twinning was observed. Uncorrected electron mobilities of 700–1000 cm2/V·sec were measured at room temperature. Intense injection electroluminescence, peaking at 2.28 eV and 2.0 eV, was observed in many diodes. Strong photoluminescence was observed in aluminum‐doped crystals at 77°K and at room temperature when irradiated with uv light.

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TL;DR: In this article, the optical absorption of island films of gold was studied as a function of island density, as determined from electron micrographs and film thickness, and the absorption band resulting from a bounded plasma resonance in the particles was shifted to longer wavelengths as the island density increased.

Abstract: The optical absorption of island films of gold was studied as a function of island density, as determined from electron micrographs and film thickness. The absorption band resulting from a bounded plasma resonance in the particles was shifted to longer wavelengths as the island density increased. The position of the band was that predicted by the Maxwell Garnett theory for island films with spherical particles. As the particles became smaller the absorption band was broadened because the mean free path of the electrons in them was reduced.

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TL;DR: In this article, the orientation distribution of all crystallites in the sample is deduced by a procedure described in a previous paper, in which the crystallite distribution function is expanded in a series of generalized Legendre functions.

Abstract: X‐ray diffraction measurements on anisotropic polycrystalline samples give a set of functions (pole‐figures) describing the orientation distribution of individual plane‐normals. From the set of these plane‐normal distributions it is possible to deduce the orientation distribution of all crystallites in the sample (inversion of pole‐figures) by a procedure described in a previous paper, in which the crystallite distribution function is expanded in a series of generalized Legendre functions. The expansion coefficients Wlmn which characterize the crystallite distribution have to satisfy restrictions imposed by the crystallographic and statistical symmetry elements existing in the sample. When the crystallites belong to the cubic crystal class, it is required not only that some of Wlmn be identically equal to zero but also that the remaining nonzero Wlmn be linearly related to each other (for given l and m). The matrix equation expressing the linear dependence among Wlmn is solved numerically by a computer an...

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TL;DR: In this article, it was shown that nucleation occurs when a cavity collapses, rather than when it expands, and that the change in pressure lowers the freezing temperature of the liquid, and thereby results in nucleation.

Abstract: Cavitation in an undercooled liquid can nucleate solid. We have demonstrated, by a new experimental technique, that nucleation occurs when a cavity collapses, rather than when it expands. Extremely large pressures, ∼105 atm, are generated by the collapse of a cavity. The change in pressure lowers the freezing temperature of the liquid, and thereby results in nucleation.It is suggested that nucleation by scratching also takes place through the medium of cavitation.

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TL;DR: In this article, the dielectric constants of CaF2, SrF2 and BaF2 single crystals were determined as a function of frequency from 102 to 106 (partly to 1010) cps, in the temperature range from −193° to 500°C.

Abstract: Dielectric constant κ′ and dielectric loss κ″ of CaF2, SrF2, and BaF2 single crystals were determined as a function of frequency from 102 to 106 (partly to 1010) cps, in the temperature range from –193° to 500°C. κ′ in all three crystals is frequency independent at 25°C. The dielectric loss κ″ varies only slightly with frequency, having the greatest values at lowest and highest frequencies. The temperature has a striking effect on κ′ and κ″. κ′ increases continuously from 6.4, 6.1, and 6.9 (extrapolated values at absolute zero) to 8.07, 7.70, and 8.46 at 500°C at frequencies above 106 cps for CaF2, SrF2, and BaF2, respectively. Below about 25°C, κ′ is frequency‐independent; at higher temperatures it increases with decreasing frequency, κ″ increases with temperature exponentially and decreases with frequency. A detailed interpretation of the frequency and temperature influence on κ′ and κ″ is given. Using expansion and density variation with temperature, a separation of electronic from atomic and dipolar contributions was made. The total dielectric constant is subdivided into six terms (three electronic and three atomic).

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TL;DR: The diffusivities of gold and silver in high-purity tin have been measured along the ''c'' and ''a'' directions in the temperature range 135°-225°C as discussed by the authors.

Abstract: The diffusivities D of gold and silver in high‐purity tin have been measured along the ``c'' and ``a'' directions in the temperature range 135°–225°C. They are described by DAu/Snc = 5.8×10−3 exp−(11 000/RT) cm2sec−1, DAu/Sna = 1.6×10−1 exp−(17 700/RT) cm2 sec−1, DAg/Snc = 7.1×10−3 exp−(12 300/RT) cm2 sec−1, and DAg/Sna = 1.8×10−1 exp−(18 400/RT) cm2 sec−1. These results are characterized by a very large anisotropy of diffusion compared with that found for the self‐diffusion of tin. Furthermore, these solutes diffuse orders of magnitude faster than the self‐diffusion of tin and also they diffuse fastest along the ``c'' direction, whereas tin diffuses fastest along the ``a'' direction. This unusual behavior is interpreted as evidence that silver and gold dissolve interstitially in tin and diffuse by an interstitial mechanism.

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TL;DR: In this article, the structure of spherulites of the monoclinic modification of isotactic polypropylene has been studied in thin films by transmission electron microscopy and electron diffraction.

Abstract: Microstructure of spherulites of the monoclinic modification of isotactic polypropylene has been studied in thin films by transmission electron microscopy and electron diffraction. Centers of spherulites are found to consist invariably of complex arrays of intercrossing lamellae. Radiating from the central regions are frondlike growths which constitute the coarse arms that are visible by optical microscopy. Each of the fronds is composed of a cluster of ribbonlike leaders, each of which, in turn, is covered with dense arrays of lamellar branches. Electron diffraction shows that constituent lamellae of both central and frondlike regions are chain‐folded single crystals. Diffraction from the central regions confirms a model proposed by Khoury in which parent and daughter branches intersect at an acute dihedral angle of 80° 40′. Morphological evidence suggests that the same branching relation is preserved in the fronds and indicates that branching is initiated on the thin (010) faces of the lamellae.

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TL;DR: In this paper, the diffusion potential and the intercept V0 of the 1/C2 vs bias plots for n-type GaP-metal Schottky-Barrier diodes have been measured.

Abstract: The diffusion potential VBO and the intercept V0 of the 1/C2 vs bias plots for n‐type GaP‐metal Schottky‐Barrier diodes have been measured. Photoresponse measurements indicate that VBO is not sensitive to the thickness δ of the interfacial separation between the GaP and the metal; V0 is observed to increase rapidly with δ. The 1/C2 plots are linear in all cases, with slopes independent of V0. The values for the donor density ND, calculated in the usual way from slopes of the 1/C2 plots, seem to agree within experimental error with ND calculated from the resistivity of the GaP.Several models are proposed for the metal‐interfacial‐layer‐semiconductor system in order to explain this behavior. The GaP‐metal diodes are shown to be best characterized by a model which includes a bias‐dependent charge in surface states at the semiconductor surface.

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TL;DR: In this article, the magnetic properties of Europium titanate have been investigated using magnetometer measurements, and it is shown that the magnetic moment (σ) increases linearly with field to 10 kOe; above 14kOe the moment saturates and σ=156 emu/gm (6.93 μB).

Abstract: Europium titanate has the cubic perovskite structure containing divalent Eu (7 μB) and tetravalent Ti. From magnetic measurements we find that EuTiO3 is one of the few antiferromagnetic materials with a positive θ (TN=5.3°K, θ=3.8°K). At 1.3°K the magnetic moment (σ) increases linearly with field to 10 kOe; above 14 kOe the moment saturates and σ=156 emu/gm (6.93 μB) at 20 kOe. Powder neutron‐diffraction work indicates that EuTiO3 has the Type G magnetic structure in which a given Eu++ has six nearest‐neighbor europium ions antiparallel and 12 next‐nearest‐neighbor europium ions parallel. In a perovskite structure where only the 12‐coordinated ion is magnetic, i.e., Eu++, the molecular field relations for a two sublattice model yield J1/k=−0.021°K, where J1 is the effective intersublattice exchange interaction, and J2/k=0.040°K, where J2 is the effective intrasublattice exchange interaction. The signs of J1 and J2 are opposite to those found in the europium chalcogenide series. The chalcogenides, however, have the rocksalt structure in which the number of 90° cation‐anion‐cation interactions differs from the perovskite structure.

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TL;DR: In this article, a simple closed-form expression for the ballistic demagnetizing factor of a uniformly magnetized cylinder was derived for p(n) ≥ 10, and the numerical extrapolation of the latter to the range 0≤p≤100.

Abstract: A simple, closed‐form expression is obtained for the ballistic demagnetizing factor of a uniformly magnetized cylinder. Detailed comparison is made between the present results and both the previously derived series expansion (in which the radial variation of magnetization is neglected), valid for p(=length/diameter) ≥10, and the numerical extrapolation of the latter to the range 0≤p≤100. An alternate derivation of a result for the magnetometric demagnetizing factor of a uniformly magnetized cylinder is presented. Detailed comparison is made between the demagnetizing factors in the uniformly magnetized cylinder (ballistic, magnetometric) and the demagnetizing factor of an inscribed ellipsoid of revolution.

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TL;DR: In this article, a high-frequency potential was applied to a metal electrode behind the dielectric target, which was used to deposit thin insulating films, achieving deposition rates up to 2000 A/min.

Abstract: Insulators cannot be sputtered with standard dc glow discharge techniques, because the accelerating potential cannot be directly applied and because the positive charge which accumulates on the surface during ion bombardment cannot be neutralized. Direct sputtering of insulators can be achieved by applying a high‐frequency potential to a metal electrode behind the dielectric target. This technique was used to deposit thin insulating films. With a properly optimized electrode configuration and a superimposed magnetic field, deposition rates up to 2000 A/min were obtained. Electrode potentials between 700 and 5500 V peak‐to‐peak were used. In all experiments described herein, the frequency was 13.56 Mc/sec and the pressure was 5×10−3 Torr. It was found that the introduction of oxygen into the argon sputtering atmosphere greatly reduced the deposition rate. Most experiments were carried out with borosilicate glass (Corning Pyrex 7740) and fused quartz. Without any special measures, films with a low pinhole density were obtained.

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TL;DR: Crossed-field electron beam stability for arbitrary values of Q /ratio of plasma frequency to cyclotron frequency was studied in this paper for any value of Q/ratio.

Abstract: Crossed-field electron beam stability for arbitrary values of Q /ratio of plasma frequency to cyclotron frequency/

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TL;DR: In this paper, the authors examined the effect of obliquely oriented cylinders on the extinction efficiency, propagation in cylindrical waveguides, and polarization reversal of the electromagnetic spectrum.

Abstract: Electromagnetic scattering by obliquely oriented cylinders, noting extinction efficiency, propagation in cylindrical waveguides and polarization reversal