摘要:

It is shown that size effect plays an important role in the ac response of hard superconductors not only at bilateral but at unilateral excitation as well. This effect manifests itself in the ac amplitude dependences of the surface impedance and absorptivity. We find that the absorptivity of a superconductor has always a prominent maximum independently of the dielectric properties of the substrate. This statement is demonstrated by theoretical calculations performed within the critical state model. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114648

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A solution route involving reactive precipitation from molten hydroxide melts is presented for the synthesis of EuBa2Cu4O8. The melt consisted of a mixture of NaOH, KOH, and Ba(OH)2, and was heated at 475 °C for ∼2 h prior to reactant addition. Eu2O3and CuO were then added, and in several hours crystallites of EuBa2Cu4O8were obtained. The product was a single phase as determined by powder x‐ray diffraction and the onset of superconductivity was observed at 78 K by dc magnetic susceptibility. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114619

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have measured the noise temperature of heterodyne receivers employing Nb/AlOx/Nb tunnel junction mixers at frequencies ranging from 70% to 93% of the gap frequency of niobium (∼700 GHz). The sensitivity of the receiver is decreased by the overlap of then=1 andn=2 photon steps of opposite sign. At bias voltages where these photon steps overlap, there is an increase in receiver noise up to 50%. Theoretical calculations using the Tucker theory agree well with the observed mixer performance. This overlap already affects the receiver operation for best performance at frequencies well below 700 GHz. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114620

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Disaccommodation and ferromagnetic resonance measurements for single crystal titanium‐doped lithium ferrites are presented. Magnetic disaccommodation is performed at 1 kHz from 77 to 400 K while ferromagnetic resonance is carried out at 11 GHz from 77 to 300 K. Ferromagnetic resonance line shape asymmetry and anisotropy field data are also shown. A relationship between the asymmetry and the disaccommodation spectra is suggested. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114621

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thin films of iron nitrides have been prepared using an ion beam assisted evaporation method. X‐ray diffraction and Mo¨ssbauer spectrometry show that the films generally consist in a mixture of Fe and Fe4N phases. For high source powers and temperatures higher than 300 °C it was possible to obtain the pure Fe4N phase. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114622

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A theoretical treatment for contrast formation in the magnetic force microscope is given which relies on calculation of the force acting on the sample, rather than the more usual method which calculates the force acting on the microscope tip. The equivalence of this reciprocal force method is demonstrated by calculating the theoretical image for longitudinal step and arctangent magnetization transitions in thin‐film recording media. The reciprocal force approach leads naturally to unambiguous definitions for the resolution of the magnetic force microscope and it is shown that conventional resolution measures, such as impulse response, line‐spread function and step response, used in many other forms of microscopy, may be readily applied to the magnetic force microscope. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114623

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In this letter, we report on the extremely narrow energy distributions that can be obtained in field emission from W and Pt nanotips. For example, the measured full width at half‐maximum for a Pt nanotip can be as low as 64 meV at 80 K and 100 meV at room temperature. Moreover, these emitted beams are autocollimated to a 4° opening and have hours of stability for a current of ∼1 nA due to the fact that the emission comes from one atom. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114624

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In narrow metal interconnects used in advanced integrated circuits, electromigration flux divergences occur at the intersection between polycrystalline cluster segments (where grain boundaries offer a fast diffusion path), and bamboo segments (where there are no grain boundaries along the line length). In confined, passivated metal interconnects, these flux divergences are linked to the evolution of significant mechanical stresses in the metal. A quasisteady state stress distribution builds up quickly in the cluster segments and remains unchanged until the stress profiles between cluster segments begin to overlap, and the clusters begin to ‘‘interact.’’ A significant increase in stress above the quasisteady state can result from cluster interactions, increasing the potential for electromigration and stress‐induced damage. If the cluster separation is small, this stress increase can occur on a time scale which is short compared to the stress evolution of the interconnect line as a whole. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114625

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated the static friction of a metal placed on ferroelectrics when an alternating current (ac) electric field was applied. Specifically, we studied the angle at which a stainless‐steel disc placed on a lead zirconate titanate (PZT) plate begins to slide, namely, the friction angle. It was found that under a constant voltage the friction angle increased as the frequency of the applied voltage was increased. A time dependency of the static friction coefficient on electrostatic force was discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114626

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.115559

出版商:AIP    

年代:1995

数据来源: AIP