摘要:

The magnetic domain structures formed at grain boundaries in recrystallized iron foils have been analyzed using Lorentz electron microscopy. Five basic types of domain structures have been observed at grain boundaries in iron: (1) Domain walls which penetrate through the boundary indicating ``no interaction,'' (2) double spike reverse domains, (3) single spike reverse domains, (4) echelon domains, and (5) domains of closure. Attempts to correlate the stability of the various domain types with the magnetic pole density of the grain boundary led to the following conclusions: (a) Double spike and ``no interaction'' domains appear to be associated with low pole densities while domains of closure appear to be associated with relatively larger pole densities and (b) no clear statement can be made with respect to the relative stabilities of the single spike and echelon domains due to difficulties in determining the magnetization direction within the domains and within the grain itself. They appear to overlap the pole densities of the other structures and each other as well. It is suggested that grain boundaries are important sources of reverse domain nucleation in polycrystalline ferromagnetic materials. The results emphasize the importance of the internal magnetostatic energy in determining the magnetic domain structure of iron.

ISSN:0021-8979    

DOI:10.1063/1.1658244

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The magnetic susceptibility has been measured for a number of NiAl compounds, ranging from 46.1 to 59.2 at.% Ni. The results were found to fit the expression, &khgr; = (A/T) +Bbetween 6° and 300°K. Calculations of the temperature independent term fit the observed composition dependence up to 50 at.% Ni, but the composition dependence of that term is much higher for Ni contents above the equiatomic composition. Similarly, the value of A remains close to zero up to 50 at.% Ni and then rises over a small composition range to a large, composition independent value. The results above 50 at.% Ni are attributed to Ni&sngbnd;Ni nearest neighbors, which cause short‐range magnetic order.

ISSN:0021-8979    

DOI:10.1063/1.1658245

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

We have performed cw resonance and pulse‐echo measurements on magnetostatic waves in short, axially magnetized YIG rods which do, and do not, contain a turning point. The results are compared with a simple theory which includes the effects of the radial variation of the demagnetizing field. The agreement is generally satisfactory except for the magnetostatic mode spacing when the rod contains a turning point. In this latter case the agreement is only qualitative.

ISSN:0021-8979    

DOI:10.1063/1.1658246

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The wide temperature range at which transitions occur between magnetic structures, and the coexistence of magnetic structures in the UP1−xSxsystem are attributed to the incomplete homogeneity of the powder samples. The inhomogeneity affects the linewidths of the x‐ray diffractometer traces, the31P nuclear magnetic resonance (NMR) lines in the paramagnetic state, and the magnetic properties of UP1−xSx. The firing treatment of UP broadens the x‐ray lines, while a second homogenization of UP0.72S0.28sharpens the x‐ray and31P NMR lines and decreases the portion of the antiferromagnetic structure that coexists with the major ferromagnetic phase at low temperatures. The composition ranges (inhomogeneity widths) deduced from the x‐ray line broadening are about 0.1x0, wherex0is the mean sulfur concentration. The upper limits of the inhomogeneity widths obtained from the excessive31P NMR linewidths and the widths of the magnetic transitions are in fair agreement with the inhomogeneity widths based on the x‐ray data.

ISSN:0021-8979    

DOI:10.1063/1.1658247

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Elastic wave velocities, particle displacement vectors, and directions of energy flux have been calculated and are given as a function of the polar angle &thgr; in the five hexagonal metals Be, Cd, Mg, Ti, and Zn. Because of elastic transverse isotropy around the hexagonal axis, the wave characteristics are functions of the angle between the hexagonal axis and the direction of propagation in the crystal only. The results of these calculations are especially useful for experimental investigations utilizing the ultrasonic pulse‐echo technique.

ISSN:0021-8979    

DOI:10.1063/1.1658248

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The orientation dependence of dislocation damping in the five hexagonal metals Mg, Cd, Be, Zn, and Ti has been predicted by calculation of the appropriate factors relating the stress field of the elastic waves to the slip systems in which the dislocations are moving. The four metals having basal slip systems have very similar qualitative behavior of the orientation factors. Titanium, with prismatic slip systems, has a quite different behavior and the orientation factors are smaller for all orientations than the values for the basal slip metals. For Zn, Cd, Mg, and Ti, the values of the orientation factors for standing waves (resonance technique) are larger than the corresponding values for the traveling waves (pulse‐echo technique). For Be, the orientation factors for both types of waves are nearly equal. Crystal orientations and wave types of particular interest for experimental study are delineated.

ISSN:0021-8979    

DOI:10.1063/1.1658249

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An experiment was carried out on the intensity distributions resulting from the superposition of the images formed in the direction of each resultant order to the diffraction and optical interference pattern of a plane amplitude grating viewing a set of slits lying in a parallel plane. The experiment demonstrated the causes of blurring of the moire´ fringes formed by two gratings separated by an air gap. From experiments conducted with pairs of identical amplitude gratings the blurring of spatial moire´ fringes is demonstrated by microdensity tracings. It was found that the optical effects did not affect the interfringe spacing of the fringes.

ISSN:0021-8979    

DOI:10.1063/1.1658250

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The time behavior of a pulse emitted by the stimulated Raman process (first vibration Stokes level in H2) is examined as a function of the Raman oscillator cavity parameter &tgr;, the photon life time. Theoretical calculations of the Raman pulse shape, including laser depletion, using a linearized model of a standing wave are provided. Experimental comparisons to the calculations demonstrate satisfactory agreement for most measurements. The experiments were performed at 100 atm of H2, in order that antistokes be suppressed and calculations simplified.

ISSN:0021-8979    

DOI:10.1063/1.1658251

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The unclamped electro‐optic coefficients were measured in ferroelectric NaNO2. The following values were obtained at 150°C, in units of 10−10cm/V:ra=r22− (n3/n2)3r32= 4.1;rb=r32− (n1/n3)3r12= 4.2;rc=r22− (n1/n2)3r12= 0.6;r43= − 1.9;r61= − 3.0. The constantsraandrcvary approximately as &egr;2does near the Curie temperature, as expected, butrbdoes not, decreasing toward zero atTc. No significant temperature dependence was found inr61orr43. The quantityrachanges sign as a function of temperature at 115°C. The observed behavior can be explained in terms of a temperature‐independent response including both second‐ and fourth‐order terms, biased by the spontaneous polarization.

ISSN:0021-8979    

DOI:10.1063/1.1658252

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The optical activity and birefringence associated with elastic and plastic deformation of alkali halide single crystals were studied by means of transmission of monochromatic light in the visible region between crossed Nichols. Below the elastic limit, the optical axis is the direction of stress application. For permanently deformed crystals, the optical axes are the [110] directions regardless of the directions of original stress application, and the associated birefringence is shown to be dependent on the modes of plastic deformation. The origin for optical activity in both elastically and plastically deformed materials is not yet clear and is probably associated with perturbation by local electric or magnetic fields of charged dislocations present in the material under investigation.

ISSN:0021-8979    

DOI:10.1063/1.1658253

出版商:AIP    

年代:1969

数据来源: AIP