摘要:

The thermomagnetic analysis of the intermetallic phases in the mischmetal‐cobalt (MM‐Co) system was used to (1) establish the identity of the structurally similar 1 : 3, 2 : 7, 5 : 19, and 1 : 5 phases by means of their distinctive Curie temperatures (<20, 61, 270, and 541 °C, respectively), (2) indicate a new magnetic transition at 340 °C between theTcof 5 : 19 and 1 : 5 phases, (3) provide unambiguous evidence for 5 : 19 and 2 : 17 phases as decomposition products of theinsitueutectoid decomposition of 1 : 5 phase, (4) confirm the existence of a homogeneity region of 1 : 5 phase withTcvarying from 487 to 520 °C with increasing Co, and (5) demonstrate the enhancement ofTcof 1 : 5 when Co replaces Fe.

ISSN:0021-8979    

DOI:10.1063/1.328040

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Measurements were made on a series of glassy iron–boron alloys to determine the association of the eutectic composition (lowest melting point) and the field‐induced magnetic anisotropy. When the boron was increased from 15 to 22 at. %, the magnetic anisotropy was found to increase from 500 to 1300 J/m3. There was no sharp discontinuity in the vicinity of the eutectic. It appears that deviation from the eutectic does not greatly influence the value of the magnetic anisotropy, provided the samples are small and are drastically quenched. Specimens having the eutectic composition had the most reproducible values of anisotropy. The substitution of silicon for some of the boron in these alloys raises their Curie and crystallization temperatures. This makes possible a greater range of heat treating temperatures and permits better stress relief in the alloys. Also, the substitution of silicon permits better control of the magnetic anisotropy. This control may be a factor in obtaining improved magnetic properties since both low coercive force and low hysteresis loss in these materials depend upon obtaining the proper value of uniaxial anisotropy. Compositions that had values of the field‐induced anisotropy of 1000 J/m3had low values of core loss when properly heat treated.

ISSN:0021-8979    

DOI:10.1063/1.328041

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The conventional expression for the exchange energy in a continuous material is valid for slowly varying functions only. It breaks down at singularities and introduces unphysical infinities. In order to correct this, it is suggested here to postulate another expression which is always finite, and can be used conveniently with functions which vary slowly over most of the material, and rapidly in some parts of it.

ISSN:0021-8979    

DOI:10.1063/1.328042

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Single‐crystal thin films of gallium‐substituted mixed garnets (Gd,Tm,Y)3(Fe,Ga)5O12, grown by liquid phase epitaxy, have been used as drive layer materials in contiguous disk bubble devices; a critical parameter for the selection of a specific composition is the value of the magnetocrystalline anisotropy constantK1. We have measured the values ofK1in a series of epitaxial thin films grown on (100) and (111) oriented gadolinium gallium garnet substrates.K1in the (100) oriented films were measured both by ferrimagnetic resonance and with an inductive hysteresigraph, whereas only resonance measurements were employed in the (111) oriented films. The values ofK1for each composition, obtained by different methods from films with different orientations, agree reasonably well with each other and are consistent with what would be expected from linear extrapolation of theK1’s of pure rare‐earth iron garnets after an empirical correction for gallium substitution.

ISSN:0021-8979    

DOI:10.1063/1.328043

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A stress‐freezing technique is used to observe the stress distribution inside a cylindrical body produced by a coaxially loaded cylindrical punch. The flat end of the punch is pressed against the top surface of a vertical cylinder. After the stress is frozen in, a thin vertical diametric slice is prepared for photoelastic observation. The stress distribution is compared with theoretical results calculated for a semi‐infinite body using the following two boundary conditions: uniform displacement of the punch and uniform pressure under the punch. The agreement is good at long distances (three times the punch radius) with either boundary condition. At short distances, the observed stress distribution is in between but close to the uniform displacement boundary condition. These results support the use of mixed stress distributions under the punch in a previous finite‐element calculation of impressing creep velocities.

ISSN:0021-8979    

DOI:10.1063/1.328044

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The theory of piezoelectric photoacoustic spectroscopy is developed for condensed‐matter samples. Treating the sample as an elastic layer and neglecting the transducer’s effect on the sample, the three‐dimensional uncoupled quasistatic thermoelastic equations are solved using a Green’s function for the stress. An expression for the dependence of the signal on absorption, modulation frequency, thermal properties, and mechanical properties of the sample is derived. The theoretical predictions are experimentally verified, the sources of noise are analyzed, and the noise equivalent power is estimated. Finally, considerations for detector optimization are discussed.

ISSN:0021-8979    

DOI:10.1063/1.328045

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The possibility of observing Raman‐inactive vibrations in solids by coherent Raman spectroscopy via the magneto‐optic effect is demonstrated. Although vibrations involving nuclei lying at a center of inversion are Raman inactive in first order, they are infrared active and therefore couple to electromagnetic radiation creating phonon polaritons. The magneto‐optic effect permits coupling of laser light to the oscillating magnetic field of the polariton mode. A theory is presented and used to calculate the effective third‐order nonlinear susceptibility for this mechanism. The magnitude is then estimated from results of Faraday rotation experiments. The effect is found to be much smaller than for most Raman‐active vibrations, yet remains within current detectable limits.

ISSN:0021-8979    

DOI:10.1063/1.328046

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Integrally colored anodic aluminum oxide consists of a mixture of Al and Al2O3. Published spectral optical properties can be quantitatively understood from an effective medium formalism, provided the Al particles are regarded as spherical and their dielectric permeability is taken to be the same as in the bulk. Implications of these requirements are discussed.

ISSN:0021-8979    

DOI:10.1063/1.328047

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The etch‐rate ratio of oxides to nonoxides in inert gas ion milling systems can be increased by injecting a flux of halocarbon gas molecules onto the surface along with the inert‐gas ion beam. In order for the halocarbon to be effective, it must adsorb on the surfaces of interest and the halogon must form a volatile reaction product with the surfaces. The system Ar+/CCl4/Si and SiO2is used to illustrate this method.

ISSN:0021-8979    

DOI:10.1063/1.328048

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

X‐ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to characterize the air‐exposed and sputter‐cleaned surfaces of glow‐discharge‐produced Si1−xCx:H (x=0.05 to 0.90) films. On the air‐exposed surfaces, silicon was preferentially oxidized with the enriched carbon existing as graphite or hydrocarbon. Signal intensities obtained from the surfaces sputter cleaned with 1 keV Ar+ion beams indicated no significant preferential sputtering of C to Si for these films. The values of the carbon 1s and silicon 2pand 2sbinding energies as well as the valence band spectra suggested a significant change in the local atomic configurations atx∼0.6–0.7. Based on these XPS and AES results and the reported IR absorption data, a slightly cross‐linked, carbon and hydrogen substituted polysilicon and an almost fully cross‐linked, silicon and hydrogen substituted polycarbon were proposed to describe the structure of films below and abovex∼0.6–0.7, respectively.

ISSN:0021-8979    

DOI:10.1063/1.328049

出版商:AIP    

年代:1980

数据来源: AIP