Showing papers in "Journal of Applied Physics in 1964"
TL;DR: In this article, the stability of a moving planar liquid-solid interface during unidirectional freezing of a dilute binary alloy is theoretically investigated by calculating the time dependence of the amplitude of a sinusoidal perturbation of infinitesimal amplitude introduced into the planar shape.
Abstract: The stability of the shape of a moving planar liquid‐solid interface during the unidirectional freezing of a dilute binary alloy is theoretically investigated by calculating the time dependence of the amplitude of a sinusoidal perturbation of infinitesimal amplitude introduced into the planar shape. The calculation is accomplished by using gradients of the steady‐state thermal and diffusion fields satisfying the perturbed boundary conditions (capillarity included) to determine the velocity of each element of interface, a procedure justified in some detail. Instability occurs if any Fourier component of an arbitrary perturbation grows; stability occurs if all components decay. A stability criterion expressed in terms of growth parameters and system characteristics is thereby deduced and is compared with the currently used stability criterion of constitutional supercooling; some very marked differences are discussed.
2,542 citations
TL;DR: In this paper, the interaction between particles and an advancing solid-liquid interface has been investigated both experimentally and theoretically, and a theory has been developed, based on the assumption that a very short-range repulsion exists between the particle and the solid.
Abstract: The interaction between particles and an advancing solid‐liquid interface has been investigated both experimentally and theoretically. For each particular type of particle, a ``critical velocity'' was observed, below which the particles are rejected by the interface, and above which they are trapped in the solid. The dependence of the critical velocity on various properties of matrix and particle was investigated. A theory has been developed, based on the assumption that a very short‐range repulsion exists between the particle and the solid. This repulsion occurs when the particle‐solid interfacial free energy is greater than the sum of the particle‐liquid and liquid‐solid interfacial free energies. The particle is pushed along ahead of the advancing interface and becomes incorporated into the solid if liquid cannot diffuse sufficiently rapidly to the growing solid behind the particle. Reasonable agreement was obtained between the calculated and experimentally observed critical velocities.
609 citations
TL;DR: In this article, the thermal conductivity of high purity SiC and impure Si and SiC has been measured over the temperature range from 3° to 300°K, and it was shown that the thermal properties of the highest purity SiCs are intermediate between those of pure Si and pure diamond, and at 300°k is greater than that of copper.
Abstract: Thermal conductivity measurements on high‐purity SiC and impure Si and SiC have been made over the temperature range from 3° to 300°K. These results show that the thermal conductivity K, of the highest purity SiC is intermediate between those of pure Si and pure diamond, and at 300°K is greater than that of copper. The heat transport in SiC is produced by phonons and these are scattered by other phonons, isotopes, and the crystal boundaries in the pure material.In impure SiC the phonons are also scattered by the electrically active impurities Al and N. These impurities reduce the K of SiC in much the same way that B and P impurities do in Si. The N impurities in natural diamonds also reduce their K below that of ideally pure diamond, but the effect is rather different since N is not electrically active.
573 citations
TL;DR: In this paper, the thermal resistivity, Seebeck coefficient, electrical resistivity and Hall mobility of GeSi alloys have been measured throughout the GeSi alloy system as functions of impurity concentration in the range 2×1018−4×1020cm−3, and of temperature in range 300°-1300°K.
Abstract: The thermal resistivity, Seebeck coefficient, electrical resistivity, and Hall mobility of Ge‐Si alloys have been measured throughout the Ge‐Si alloy system as functions of impurity concentration in the range 2×1018−4×1020cm−3, and of temperature in the range 300°–1300°K. A qualitative interpretation of these properties is given. For power conversion, boron and phosphorus were found to be useful p‐type and n‐type impurities, respectively, because of their high solid solubilities. At 1200°K, the maximum values of the dimensionless figure of merit zT were 0.8 for p‐type Ge0.15‐Si0.85 alloy doped to 2.1×1020cm−3 holes, and 1.0 for n‐type Ge0.15‐Si0.85 alloy doped to 2.7×1020cm−3 electrons. The maximum over‐all efficiency of a stable generator operating between 300°–1200°K, using the best p‐type and n‐type materials was computed to be 10%.
556 citations
TL;DR: In this paper, the solubilities of substitutional and interstitial copper (Cus and Cui) have been measured in intrinsic and extrinsic n and p-type Ge, Si, and GaAs, using Cu64.
Abstract: The solubilities of substitutional and interstitial copper (Cus and Cui) have been measured in intrinsic and extrinsic n‐ and p‐type Ge, Si, and GaAs, using Cu64. These measurements show that Cus is a triple acceptor in both Ge and Si, and that Cui is a single donor in all three semiconductors. Charge compensation experiments show that Cus is a double acceptor in GaAs. In intrinsic semiconductor near 700°C the ratios of substitutional to interstitial solubilities are 6, ∼10−4, and 30, respectively. Electrically active donors due to Cui have been observed in Si by Hall‐effect measurements. Pairing between Cus and donors is pronounced in n‐type Ge but relatively unimportant above 600°C in Si. There is no evidence for pairing between Cui and acceptors in any of these semiconductors.The interstitial diffusion coefficient Di is independent of doping in extrinsic p‐type material. At 500°C, Di=2.8, 0.76, and 1.0×10−5 cm2/sec with activation energies of 0.33, 0.43, and 0.53 (±10% in each case) eV, respectively. D...
550 citations
TL;DR: In this paper, a systematic study of impurity segregation in spherulitic crystallization is described, in which the role of impurities is fulfilled by stereoirregular molecules or by molecules of low molecular weight.
Abstract: A systematic study of impurity segregation in spherulitic crystallization is described. The experiments deal principally with high polymers, in which the role of ``impurities'' is fulfilled by stereoirregular molecules or by molecules of low molecular weight. It is shown that these species are rejected preferentially by growing crystals and that their diffusion plays a vital part in governing over‐all morphology. In particular, openness of texture is related to the concentration of impurity present; and coarseness of texture, which is a measure of the ``diameters'' of crystalline fibers between which impurities become concentrated during crystallization, is determined by δ=D/G, where D is the diffusion coefficient in the melt and G is the radial growth rate of the spherulite. Results provide substantial support for a theory of spherulitic crystallization proposed by the authors.
537 citations
TL;DR: The lattice parameters of single-crystal SrTiO3 were determined by x-ray diffraction as a function of temperature from 42° to 300°K.
Abstract: The lattice parameters of single‐crystal SrTiO3 were determined by x‐ray diffraction as a function of temperature from 42° to 300°K In addition to the normal cubic structure three significant regions were found From 65° to 100°K a tetragonal modification exists (c/a=100056), from 35° to 55°K line splitting consistent with orthorhombic symmetry was observed, and at 10°K an anomalous maximum in the lattice parameter vs temperature curve was found which suggested a third structure transformation In the tetragonal region (at 78°K) various domain configurations were photographed with a polarizing microscope
422 citations
TL;DR: In this paper, the results of ZnSe, ZnTe, and CdTe were obtained from prism refraction data and reported for a series of wavelengths from 2.5 μ to the short-wave transmission limits set by the band gaps.
Abstract: Refractive indexes of ZnSe, ZnTe, and CdTe were obtained from prism refraction data and are reported for a series of wavelengths from 2.5 μ to the short‐wave transmission limits set by the band gaps. The results were fitted with the standard formula: n2=A +[Bλ2/(λ2−c2)] where n is the refractive index and λ is the wavelength in microns. For ZnSe the best values of the parameters are A=4.00, B=1.90, and c2=0.113; for ZnTe, A=4.27, B=3.01, and c2=0.142; and for CdTe, A=5.68, B=1.53, and c2=0.366. Possible causes for the discrepancies between the present results and earlier data are discussed.
407 citations
TL;DR: In this article, the authors discuss the applicability of the seventeen two-dimensional space groups and the eighty diperiodic groups in three dimensions to the description of a surface structure relative to a triperiodic substrate.
Abstract: The recent increase of activity in the field of slow‐electron diffraction has resulted in a need for agreement on conventions of terminology in the description of a diperiodic surface structure relative to a triperiodic substrate. Vector description of the surface structure net in terms of the substrate surface net is suggested. Fractional Miller indices result when the surface structure mesh is larger than the substrate surface mesh. The surface structure may be either that of a deposit or that of the selvedge of the substrate.With the relaxation of one of the diffraction conditions in the diperiodic structure the reciprocal lattice becomes a set of parallel rods intersecting the Ewald sphere continuously with change of wavelength of the incident radiation or change of orientation of the crystal.The paper discusses the applicability of the seventeen two‐dimensional space groups and the eighty diperiodic groups in three dimensions to these diperiodic structures. A comparison is made between the different ...
329 citations
TL;DR: In this paper, the refractive index of GaAs, as measured by the prism refraction method, is reported for photon energies from 0.7 eV up to the absorption limit set by the band gap, for temperatures of 300°, 187°, and 103°K.
Abstract: The refractive index of GaAs, as measured by the prism refraction method, is reported here for photon energies from 0.7 eV up to the absorption limit set by the band gap, for temperatures of 300°, 187°, and 103°K. The results are compared with the previous data (obtained only for room temperature), and are used to show that the spacing of emission lines of GaAs lasers corresponds to that of the axial modes of a Fabry‐Perot resonator.
310 citations
TL;DR: In this paper, the redistribution of impurities during thermal oxidation of silicon was studied both theoretically and experimentally, and it was shown that the redistribution process can be significantly influenced by the escape of impurity through the oxide layer as well as by the segregation of the impurity at the oxide-silicon interface.
Abstract: The redistribution of impurities during thermal oxidation of silicon was studied both theoretically and experimentally. Experiments with specific impurities indicate that gallium, boron, and indium deplete from silicon, while phosphorus, antimony, and arsenic pile up during thermal oxidation. It is shown that the redistribution process can be significantly influenced by the escape of impurities through the oxide layer as well as by the segregation of the impurity at the oxide‐silicon interface.
TL;DR: In this article, the authors measured velocities and elastic moduli for high purity silicon (resistivity ∼400 Ω−cm) as a function of hydrostatic pressure and temperature in the ranges 0 −30 000 psi (0 −2100 kg/cm2) and − 195.8° to 25°C.
Abstract: Ultrasonic wave velocities and elastic moduli for high purity silicon (resistivity ∼400 Ω‐cm) have been measured as a function of hydrostatic pressure and temperature in the ranges 0–30 000 psi (0–2100 kg/cm2) and − 195.8° to 25°C. Variations of moduli with pressure are found to be nearly independent of temperature in the range listed. For 25°C(Δc11/Δp)=4.33, (Δc12/Δp)=4.19, (Δc44/Δp)=0.80, (ΔK/Δp)=4.24. For − 195.8°C(Δc11/Δp)=4.29, (Δc12/Δp)=4.20, (Δc44/Δp)=0.75, (ΔK/Δp)=4.23.
TL;DR: In this article, the influence of impurity segregation on the kinetics of spherulitic crystallization is examined, and it is shown that transport processes within regions extending some distance from solid liquid interfaces play a major part in controlling growth kinetics.
Abstract: The influence of impurity segregation on the kinetics of spherulitic crystallization is examined. Radial growth rates over a range of temperatures are reported for a number of polymers containing various proportions of impurity species of widely varying molecular weight. Variations of growth rate with molecular weight indicate that transport processes within regions extending some distance from solid‐liquid interfaces play a major part in controlling growth kinetics. In the unusual case of a polymer containing impurities of very low molecular weight, extended radial diffusion of impurities may even give rise to parabolic growth [(radius) ∝ (time)½] in place of linear growth as normally found. Conventional interpretations fail to account satisfactorily for dependence on molecular weight, and are clearly inadequate in that they deal with transport processes only as ``jump'' processes at these interfaces. Complications that transport processes within the body of the melt introduce into the problem of formulating an absolute theory of growth kinetics are discussed.
TL;DR: In this article, the thermal J•V characteristic for a tunnel junction is derived in terms of a generalized theory, and the resulting functional form of the equations is similar to that of Stratton; however, in the present formulation, the physical parameters of the junction appear explicitly and their effect upon the thermal characteristic is readily appreciated.
Abstract: The thermal J‐V characteristic for a tunnel junction is derived in terms of a generalized theory. The resulting functional form of the equations is similar to that of Stratton; however, in the present formulation, the physical parameters of the junction appear explicitly, and their effect upon the thermal characteristic is readily appreciated. In Stratton's work, the physical constants appear in the integrand of integral that can be solved only numerically.The theory is applied to symmetric and asymmetric junctions. For the symmetric case, it is shown that, at a given temperature, the percentage change Ĵ in the high‐temperature thermal component of current from the low‐temperature value increases initially with increasing voltage bias up to a maximum peak, and thereafter decreases rapidly. The voltage bias at which the component of thermal current maxima occurs is equal to the interfacial barrier height and, as such, permits what is probably the most accurate method of barrier height determination. Simila...
TL;DR: In this article, the adiabatic elastic moduli of single crystals of aluminum have been measured from 4.2° to 300°K by using the ultrasonic pulse-echo technique.
Abstract: The adiabatic elastic moduli of single crystals of aluminum have been measured from 4.2° to 300°K by using the ultrasonic pulse‐echo technique. The values obtained by extrapolation to 0°K are C11=11.430, C12=6.192, and C44=3.162 in units of 1011 dyn/cm2. The Debye temperature obtained from the 0°K modulus values is 430.3°K, in excellent agreement with the value from heat‐capacity measurements.
TL;DR: In this article, it was found by chemical etching, by examination for a twist associated with a screw dislocation, and by observations in the electron microscope, that both ribbons and needles of small dimensions are free of dislocations and imperfections.
Abstract: The preparation from vapor and the structure of filamentary crystals of silicon have been studied in detail. It was found by chemical etching, by examination for a twist associated with a screw dislocation, and by observations in the electron microscope, that both ribbons and needles of small dimensions are free of dislocations and imperfections. Certain impurities such as gold, nickel, or platinum, however, are essential for the growth of filamentary crystals.The growth of micron size and larger whisker crystals from the vapor takes place in two stages. The first is a rapid extension in length of a leader‐like crystal of small cross section; the second, a slow thickening of the leader through deposition on lateral faces. Initial growth is associated with impurities and does not require an axial screw dislocation. Subsequent growth may be explained by classical nucleation at a step and lateral translation of the step.
TL;DR: In this paper, the shape of the potential barrier existing between two parallel-plane metal electrodes separated by a thin insulating film is discussed in detail, and the emission-limited current flow between the electrodes is determined for symmetric and asymmetric junctions.
Abstract: This paper discusses in detail the shape of the potential barrier existing between two parallel‐plane metal electrodes separated by a thin insulating film The emission‐limited current flow between the electrodes is determined for symmetric and asymmetric junctions The asymmetric J‐V (current‐voltage) characteristic is of particular interest, as it can be shown that the difference in work function of the two electrodes comprising the junction can be obtained from a perfunctory study of the characteristic The thermionic J‐V characteristic is compared to the tunnel J‐V characteristic For a temperature of 300°K, and for a barrier thickness less than 40 A, the tunnel J‐V characteristic predominates However, for barrier thickness greater than 40 A, either the thermionic or the tunnel characteristic can predominate, depending upon the barrier height and the applied voltage In the case of asymmetric junctions, there may be a reversal of direction of rectification with decreasing temperature This reversal of rectification may explain the similar effect sometimes observed in tunnel junctions
TL;DR: In this article, the magnetic ripple of thin films with uniaxial anisotropy is calculated for the field and the magnetization lying along the easy and the hard direction of the uni-cial anisotropic waveform.
Abstract: The magnetic ripple of thin films with uniaxial anisotropy is calculated for the field and the magnetization lying along the easy and the hard direction of the uniaxial anisotropy. For small dispersion of the direction of magnetization, the variational principle, applied to all energy terms including the exchange, crystalline anisotropy, uniaxial anisotropy, magnetostriction, magnetostatic, and stray field energies, yields a Bessel's differential equation. Its solutions (cylindrical functions) describe the two‐dimensional magnetic ripple of the film. Along the mean direction of the magnetization the fluctuations of the magnetization vector are much greater than perpendicular to it. In the first case these fluctuations are coupled by exchange forces, and in the second case by the stray field. The dispersion of the magnetization depends on the dispersion of the anisotropy, on the magnetic constants of the film, on the thickness of the film, and on the applied field. The theory is able to explain the image o...
TL;DR: In this article, the thermodynamic theory of substances which are ferroelectric and ferromagnetic simultaneously are given in the case of solid solutions based on BiFeO3, which has a perovskite-type structure.
Abstract: Magnetic and electric properties of some single crystals of complex composition of perovskite‐type structure were investigated and coexistence of ferroelectric and antiferromagnetic properties was shown in them. It was found that single crystals YMnO3 and YbMnO3 of the new class of ferroelectrics, discovered by Bertaut and others, are also antiferromagnetics. The results of the investigation of solid solutions based on BiFeO3, which has a perovskite‐type structure, are discussed. The opinion is expressed that BiFeO3 is probably not a ferroelectric. The main results concerning the thermodynamic theory of substances which are ferroelectric and ferromagnetic simultaneously are given in this report.
TL;DR: In this paper, a simple model containing two constants: extrapolated breakdown voltage Vb and series resistance Rs; and two continuous probability functions: turnoff probability per unit time p10(I) as a function of pulse current I and turn on probability p01 p01.
Abstract: The complex current fluctuations observed in connection with microplasma breakdown can be explained by a simple model containing two constants: extrapolated breakdown voltage Vb and series resistance Rs; and two continuous probability functions: turnoff probability per unit time p10(I) as a function of pulse current I and turn‐on probability per unit time p01 Experimental methods allowing an accurate measurement of these four quantities are described The new concept of an extrapolated breakdown voltage Vb is discussed based on two independent measurements: one of secondary multiplication and the other of instantaneous current, both as a function of voltage Within the experimental accuracy of 20 mV both methods extrapolated to one and the same breakdown voltage The turnoff probability p10(I) is determined by a new combination of experimental techniques to cover the current range from 5 to 70 μA with a variation of 11 decades for p10(I) The observation of a narrow turnoff interval is explained quantitatively
TL;DR: In this article, Brugger et al. used ultrasonic wave propagation to determine the third-order moduli of a single crystal by means of ultrasonic frequency-wave propagation, and showed that the results for silicon and germanium demonstrate a good degree of self-consistency.
Abstract: Experimental techniques for determining third‐order moduli of single crystals by means of ultrasonic wave propagation are described. Results for silicon and germanium demonstrate a good degree of self‐consistency among the basic experimental data obtained with both hydrostatic and uniaxial pressure.In units of 1012 dyn/cm2 and for 25°C, the third‐order moduli are: ModulusValue for SiValue for GeC111−8.25±0.10−7.10±0.06C112−4.51±0.05−3.89±0.03C123−0.64±0.10−0.18±0.06C144+0.12±0.25−0.23±0.16C166−3.10±0.10−2.92±0.08C456−0.64±0.20−0.53±0.07 Thermodynamic definitions for the moduli (K. Brugger, Phys. Rev. 133, A1611 (1964)] have been used.
TL;DR: In this article, ultrasonic attenuation measurements were made from 2 to 100 Mc/sec in the pearlitic plus-ferritic, bainitic, and martensitic transformation products in SAE 4150 steel, a low alloy, 0.5% carbon variety.
Abstract: Ultrasonic attenuation measurements were made from 2 to 100 Mc/sec in the pearlitic‐plus‐ferritic, bainitic, and martensitic transformation products in SAE 4150 steel, a low‐alloy, 0.5% carbon variety. Measurements were also made in the martensitic specimen after tempering. Ultrasonic velocity measurements were made at 10 Mc/sec in each case. To eliminate the question of grain size and grain size distribution, three specimens were treated identically through the austenitizing operation. Then they were cooled differently to produce the three transformation products. The attenuation can be expressed as Af4+Cf2, where f is frequency. The first term is Rayleigh scattering and the second may be from dislocation damping, atomic relaxations, or magnetic domain boundary effects. Both A and C are strong functions of microstructure. Both coefficients decrease in the order pearlite‐plus‐ferrite, bainite, martensite, tempered martensite. On tempering, A decreased in the ratio 3:2 while C decreased 3:1. In pearlite‐plus‐ferrite, A is larger by a factor of 225 than it is in tempered martensite, and C is larger by a factor of 10. The ratio CT/CL (T = transverse waves, L=longitudinal waves) was a constant independent of microstructure and equal to 2.4. This suggests either dislocation damping, an atomic relaxation, or a magnetic effect. The large change in C on tempering (with CT/CL = constant) indicates that the interstitial carbon is involved. The ultrasonic velocity measurements showed an increase in velocity on tempering the martensite. Pearlite‐plus‐ferrite has the highest velocities and density, while raw martensite has the lowest. The differences in velocities arise primarily from differences in the elastic moduli of the transformation products, not from the density differences.
TL;DR: In this article, photoelectric measurements of the bias dependence of the potential energy barrier for electrons in gold n-type silicon Schottky diodes show that the image force dielectric constant deduced from direct measurement of the barrier lowering is 12.0±0.5.
Abstract: Photoelectric measurements of the bias dependence of the potential energy barrier for electrons in gold n‐type silicon Schottky diodes show that the image force dielectric constant deduced from direct measurement of the barrier lowering is 12.0±0.5, in close agreement with the infrared dielectric constant of silicion, and independent of the applied field for fields between 104 and 2×105 V/cm. The current‐voltage characteristics of these diodes at room temperature cannot be explained on the basis of pure Schottky emission.
TL;DR: In this paper, it was shown that the hydrodynamical behavior of incompressible second-order fluids is determined by three material constants: η0, β, γ, besides the density.
Abstract: In the general theory of the behavior of simple fluids with fading memory in slow deformations, the constitutive equation of those fluids called second‐order fluids gives to the equation of Newtonian fluids a correction for viscoelastic effects that is complete to within terms of order greater than two in the time scale. The hydrodynamical behavior of incompressible second‐order fluids is determined by three material constants: η0, β, γ, besides the density. We show here that not only the viscosity η0, but also the constant γ which governs certain normal stress effects, is determined by the shear‐relaxation modulus of classical infinitesimal viscoelasticity. This result enables us to show that in a slow Couette flow the viscoelastic contribution to the difference in normal thrusts on the inner and outer cylindrical walls has a sign opposite to that of the inertial contribution. We also suggest several practicable methods for measuring β and γ.
TL;DR: A unified theory of the thermomechanical behavior of viscoelastic media is developed from studying the thermodynamics of irreversible processes, and includes discussions of the general equations of motion, crack propagation, and birefringence.
Abstract: A unified theory of the thermomechanical behavior of viscoelastic media is developed from studying the thermodynamics of irreversible processes, and includes discussions of the general equations of motion,crack propagation, and birefringence. The equations of motion in terms of generalized coordinates and forces are derived for systems in the neighborhood of a stable equilibrium state. They represent a modification of Biot's theory in that they contain explicit temperature dependence, and a thermodynamically consistent inclusion of the time‐temperature superposition principle for treating media with temperature‐dependent viscosity coefficients. The stress‐strain‐temperature and energy equations for small deformation behavior follow immediately from the general equations and, along with equilibrium and strain‐displacement relations, they form a complete set for the description of the thermomechanical behavior of media with temperature‐dependent viscosity. The role of thermodynamics in finite deformation and crack propagation problems is examined. Restrictions placed on the constitutive equations by thermodynamics is illustrated by considering a familiar stress‐strain equation for polymers, wherein the time and strain dependence of stress in a relaxation test appear as separate factors. In addition, an energy equation for crack propagation is derived and then applied to a specific problem. Thermodynamic implications concerning birefringence are also discussed and an operational stress‐optical coefficient is derived.
TL;DR: In this paper, three crystalline modifications of isotactic polybutene have been obtained from dilute solution in a variety of habits: tetragonal, hexagonal, and orthorhombic.
Abstract: Three crystalline modifications of isotactic polybutene‐1 have been obtained from dilute solution in a variety of habits. These three crystalline modifications are: (a) tetragonal, (b) ``untwinned'' hexagonal, and (c) orthorhombic. The structure of the orthorhombic polymorph has not previously been reported. The basic morphology of all forms is the thin lamellar structure associated with polymer single crystals containing folded chains. A crystal‐crystal transformation (from tetragonal to ``twinned'' hexagonal) was observed to occur when single crystals were allowed to stand at room temperature. This transformation involved a conformational change (from an 113 helix to a 31 helix), as well as the crystallographic one, but it did not involve a morphological change. No change in either morphology or crystallography occurred at room temperature in the orthorhombic or the ``untwinned'' hexagonal polymorphs, although both could be transformed completely into the tetragonal form if dried crystals were heated at...
TL;DR: The europium chalcogenide series all have the rocksalt structure, the oxide, sulfide, and selenide being ferromagnetic, and it is on these materials that the most work has been done.
Abstract: Ferromagnetism has been found in several divalent europium compounds. Some of these materials are particularly simple in both crystal and magnetic structure and are ideal for experimental and theoretical study. The materials we have investigated can be divided into three groups, europium chalcogenides, europium halogens, and europium silicates. Magnetic information on these compounds are summarized and theoretical results reviewed.The europium chalcogenide series all have the rocksalt structure, the oxide, sulfide, and selenide being ferromagnetic, and it is on these materials that the most work has been done. This is especially true of EuS where detailed moment, specific heat, and nuclear magnetic resonance measurements are available. The oretical analysis indicates that there is positive exchange between nearest‐neighbor europium atoms which decreases with increasing atom spacings. There is also a weaker negative superexchange via the anions in these compounds which is responsible for antiferromagnetism...
TL;DR: In this article, the magnetic properties of a single crystal disk irradiated with neutrons at 295°C, with an applied magnetic field along the [100] direction, were studied and it was shown that after irradiation the sample is made of small ordered crystallites with their tetragonal axes distributed along a [100], [010], or [001] direction.
Abstract: It has been shown that a new ordered structure can be obtained in an Fe‐Ni (50%–50%) alloy, by irradiating it with neutrons below 320°C. This ordered structure is tetragonal (AuCu type) and leads to a very high magnetic anisotropy. We have studied the magnetic properties of a single‐crystal disk irradiated with neutrons at 295°C, with an applied magnetic field along the [100] direction. The x‐ray superlattice lines show that after irradiation the sample is made of small ordered crystallites with their tetragonal axes distributed along a [100], [010], or [001] direction. The study of the anisotropy energy in the sample plane [011], and the magnetization curves drawn for different directions, show that this sample presents the characteristics of a uniaxial substance. But if we express, in a classical way, the anisotropy energy by K1 sin2θ+K2 sin4θ, we find experimentally K1=3.2·106 ergs/cm3 and K2=2.3·106 ergs/cm3.This high value of K2 is not in agreement with the conception of independent crystallites. One...
TL;DR: In this article, the authors obtained energy distributions for atoms sputtered from Cu (100), (110), (111), and polycrystalline surfaces bombarded by 80 to 1200 eV Hg and noble gas ions.
Abstract: Energy distributions have been obtained for atoms sputtered from Cu (100), (110), (111), and polycrystalline surfaces bombarded by 80‐ to 1200‐eV Hg and noble gas ions. Energies of sputtered atoms are found to depend markedly on the angle of ejection. For a (110) surface bombarded by 1000‐eV Kr ions, average energies of ejected atoms are 9.5 eV in the [110] direction (normal to the surface) and 14.2 eV in the [011] direction (60° to the surface normal). Ejection energies decrease for lighter ions in the order Kr+, Ar+, Ne+, and He+. For a (110) surface bombarded by 600‐eV He ions, the average energy of atoms ejected in the [110] direction is 5.5 eV. Dependence on bombarding ion energy is very weak above 1000 eV where average energies of sputtered atoms are found to be in the range 5–15 eV. Ejection energies decrease at lower bombarding ion energies and decrease rapidly below 200 eV. For atoms ejected in the [110] direction from a (110) surface under Kr ion bombardment, the average energy decreases from 5.5 eV at an ion energy of 200 eV to 2.6 eV at an ion energy of 80 eV.