摘要:

The hyperfine field structure and magnetic susceptibility in the temperature range 5–295 K was measured for the &bgr;&prime3; phase of potassium ferrite. Results show that this new phase has an antiferromagnetic ordering similar to the &bgr; phase. The hyperfine‐interaction parameters have been determined and are compared with those found in magnetite, &bgr;‐phase potassium ferrite, and barium hexaferrite.

ISSN:0021-8979    

DOI:10.1063/1.325739

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This paper presents the results of an experimental study of the propagation characteristics of magnetoelastic‐surface waves (MESW’s) on the (011¯) surface of a 1.5×0.1‐cm2YIG disk and on the (111¯) surface of a 5.1‐&mgr;m YIG film, and a quantitative analysis of the results. Magnetoelastic‐surface waves were excited and detected by means of meander‐line transducers which were fabricated through standard photolithography techniques. The waves were excited so as to propagate along [100] and [011] directions on the disk and along the [011] direction on the film. Strongest excitation occurred for the magnetic bias field tangential to the surface and parallel to the direction of propagation. The propagation characteristics were studied at 143.5, 235, and 440 MHz. In addition to the MESW mode, other magnetoacoustic modes, which were stronger than the MESW mode under certain conditions, were also observed. Under certain conditions, as many as a dozen of these other modes, with a wide range of velocities both faster and slower than the MESW’s, were observed. Waves propagating along the [100] direction showed a distinct MESW mode. For the lower frequencies the MESW was the strongest mode excited; at higher frequencies some of the other modes were as much as 5 dB stronger than the MESW mode. For propagation along the [011] direction, the MESW was present, but was always accompanied by other strong magnetoacoustic modes with nearly the same propagation velocity. The strength of both types of modes increased rapidly with excitation frequency, in qualitative agreement with the theory of meander‐line excitation. Between 70 and 440 MHz excitation efficiency increased by nearly 30 dB. The experimental results on the disk show that the magnetic bias field required to produce the minimum insertion loss for propagation in the [100] direction was always larger than the bias field for propagation in the [011] direction. An analysis of magnetostatic resonance predicts a difference in the bias field for the two directions of propagation consistent with the measured values. Stripe domains were observed with at least two stable directions in the YIG film. The period of the domains was approximately 4 &mgr;m. MESW’s were excited and detected at a magnetic bias field for which a domain structure had disappeared. These observations differ from those of Volluetetal.

ISSN:0021-8979    

DOI:10.1063/1.325740

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The precipitation process of nickel ferrite (NiFe2O4) from silicate glasses has been studied by electron spin resonance (ESR). The ESR linewidth &Dgr;H1/2and effectivegvalue were measured as functions of heat‐treatment temperature and time. Both the linewidth and effectivegvalue change drastically near the glass transition temperature and precipitation temperature. The results are interpreted on the basis of the development of ion ordering, i.e., magnetic‐order development, that occurs during the heat treatments.

ISSN:0021-8979    

DOI:10.1063/1.325741

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A method of obtaining activation energy spectra from thermally stimulated currents is described. It is based on Primak’s analysis for the relaxation in a system distributed in activation energy and based on an interpretation of the initial rises of thermally stimulated currents using the distribution of activation energy. The method is applied to the thermally stimulated current of polycarbonate.

ISSN:0021-8979    

DOI:10.1063/1.325742

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The influence of doping with Al and some iron‐group metals on optical and electrical properties of GaN epitaxially grown from the vapor phase is reported. These impurities are the main inadvertent contaminants in GaN growth, and details on the transport of these elements to the deposition area during growth are discussed. Detailed studies are performed by the SIMS technique on impurity concentration in layers grown under different conditions of contamination. Variations in doping over the area of the grown wafers, as well as with depth into the layer, are investigated, and shown to be significant for Al and N2. These investigations are complemented by SEM cathodoluminescence topographs. Photoluminescence data strongly indicate the existence of a shallow bound exciton (binding energy 12 meV) to isoelectronic Al on Ga sites in GaN. No radiative states are observed from the iron‐group contaminants. These (notably Fe and Cr) cause deep states efficient in electrical compensation of the material, which is easily made highly resistive with Fe or Cr.

ISSN:0021-8979    

DOI:10.1063/1.325743

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Emission cross sections of a Nd stoichiometric laser crystal LiNdP4O12at 1.048 &mgr;m were measured by a direct absorption method and the conventional spectroscopic method. The largest effective‐emission cross section was determined to be &sgr;beff= (1.7±0.2) ×10−19cm2by these two methods. Emission cross sections of NaNdP4O12, KNdP4O12and LiNd0.1Ln0.9P4O12(Ln=Gd, La) were also determined by the conventional spectroscopic method. The radiative lifetime of LiNdP4O12was calculated from the fluorescence spectra and the quantum efficiency of LiNdP4O12was found to be 0.34.

ISSN:0021-8979    

DOI:10.1063/1.325744

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The charge‐generation energy for commerical selenium xeroradiographic plates has been measured. A new technique based on x‐ray‐induced photocurrents was used as well as conventional xeroradiographic discharge measurements. Using x‐ray spectra typical of medical x‐ray irradiations at a conventional applied field of 10 V/&mgr;m, a charge‐generation energy of 30–40 eV per pair was determined. Theoretical estimates related to the band gap predict a pair‐creation energy of 7 eV per pair for selenium.

ISSN:0021-8979    

DOI:10.1063/1.325745

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The optical properties of bulk and thin‐film Zn3P2have been measured at room temperature over the range 0.5–5.0 eV, with emphasis on the region of the interband absorption edge. The bulk absorption edge is found to be exponential in energy for values of absorption coefficient less than about 1500 cm−1. The thin‐film absorption edge, when freed of spurious absorptance due to scattering, is also found to be exponential over this range although shallower in slope. Analysis of the thin‐film data at higher values of absorption coefficient is inconclusive with respect to the nature of the edge. Nevertheless, indirect evidence suggests that the optical gap is probably direct and lies in the neighborhood of 1.6 eV. Measurements of refractive index in the near‐infrared yieldn=3.3±0.1 in the long‐wavelength limit. The ultraviolet reflectivity spectrum is redetermined, and found to differ substantially from earlier reports. Results are discussed in terms of the Dow‐Redfield model of exponential absorption edges, the effects of spin‐orbit and crystal‐field splittings, and effects arising from the equilibrium distribution of bond lengths peculiar to this material. It is concluded that the optical properties of Zn3P2thin films are suitable for use in photovoltaic cells, provided antireflection coatings are employed.

ISSN:0021-8979    

DOI:10.1063/1.325746

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Secondary negative and positive charge emission coefficients for bombardment of a gas‐covered Cu surface by H+, H0, and H−have been measured for projectile energies of ∼25–2500 eV. The secondary negative charge yield for H0impact was found to be 1.15±0.08 times that for H+impact. For H−impact, the secondary negative charge yield decreased less rapidly with projectile energy than that of H+and H0impact, being about an order of magnitude larger at the lowest energies investigated. The secondary positive charge yields were found to be independent of the projectile charge state and were about an order of magnitude smaller than the negative charge yields. The measurement techniques are described, and the results are compared with the data of other investigators.

ISSN:0021-8979    

DOI:10.1063/1.325747

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Deposition profiles calculated for a hexagonal array of point sources were used to determine the optimum spacing of components in composite sputtering targets. The results showed that smooth deposit‐thickness profiles and homogeneous alloys could be expected for a point spacing of one‐half the source‐to‐substrate distance and that deposit‐thickness variations had nearly the same spacing dependence as had been calculated earlier for parallel strip sources. A Ag‐0.5 at.% Pu sputter deposit made from such a hexagonal‐array composite target was found indeed to be homogeneous by autoradiographic analysis of the Pu distribution in the deposit. The results for both point and strip sources suggest that vapor deposition will homogenize any inhomogeneous composite source if the spacing of the inhomogeneity is less than one‐half the source‐to‐substrate distance. Thus, vapor deposition can be used to chemically homogenize alloys.

ISSN:0021-8979    

DOI:10.1063/1.325748

出版商:AIP    

年代:1979

数据来源: AIP