AES , — IEEE 69 , — Dinger, R. Fano, R. Franklin Institute , 57—83, — Khamas, S. Chaloupka H. Mitola, J. Wepman, J. IEEE Int.
Microwave Properties and Applications of High Temperature Superconductors
Personal , Indoor and Mobile Radio Comm. Warr, P. Gevorgian, S. Oates, D. Leeson, D. IEEE 54 , — Ghosh, I. Wilker, C. Kudsia, C. Amott, R. Gibson J. Kohno, R. Zander, J. Aminov, B. Litva J. Norwood,MA: Artech House. Chaloupka 1 1. University of Wuppertal Wuppertal Germany. Personalised recommendations. Cite chapter How to cite? ENW EndNote. The book will appeal to researchers in electrical and electronic engineering.
Help Centre. My Wishlist Sign In Join. Be the first to write a review. Add to Wishlist. Ships in 10 to 15 business days. Link Either by signing into your account or linking your membership details before your order is placed. Description Table of Contents Product Details Click on the cover image above to read some pages of this book! Preface Acknowledgements Superconductivity at microwave frequencies Superconducting transmission lines Superconducting cavity resonators Microwave measurements Superconducting filters Superconducting delay lines Superconducting antennas Signal processing systems The surface impedance of HTS materials Substrates for superconductors Some useful relations Table of Contents provided by Publisher.
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In Stock. The rf magnetic field is parallel to the DC field of the solenoid, which yields the largest vortex motion induced absorption according to the CC theory The microwave loss decreases rapidly below T c in zero magnetic field as expected for superconductors. The most important observation is that the microwave loss becomes significant for a magnetic field as small as 0. In fact, we observe a giant , about a factor 3 times larger, microwave absorption below T c than in the normal state.
This striking difference between the crystal and fine grain samples is clearly demonstrated for K 3 C 60 where measurements on both kinds of samples are shown. For MgB 2 , microwave measurements on compacted samples or surface impedance measurements supports this observation as therein no enhanced microwave absorption was observed 41 — Note that the cavity loss changes significantly for the powder sample in contrast to the single crystal sample.
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We believe that the enhanced microwave absorption is an ubiquitous property of fine powders of type-II superconductors. We therefore focus on K 3 C 60 in the following. The enhanced microwave loss appears progressively with increasing magnetic field additional data are shown in the Supplementary Material. The zero magnetic field data also shows a small peak invisible at the scale of Fig. This small peak is not due to magnetic field and is most probably a tiny conductivity coherence peak the analogue of the Hebel—Slichter peak 50 which is known to be strongly suppressed by strong-coupling effects in alkali fullerides 51 , While the presence of a coherence peak itself is an interesting physical phenomenon 3 , 53 , it is not relevant for the present discussion.
The fact that the enhanced microwave absorption occurs with the application of the magnetic field hints at a flux motion related phenomenon that is discussed in the framework of the CC theory.
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The microwave absorption peak occurs above the irreversibility line, i. The strong dependence on the sample morphology is also discussed below. This leads to:. We have implemented the calculation details are given in the Supplementary Material and validated our calculations by comparing the results to that published in ref. Here, we discuss qualitatively the predictions of the CC theory and some typical cases are shown in Fig. It is worth noting that this result is formally analogous to the AC Drude model as the underlying equation of motion of electrons or vortices is the same. The CC theory allows to quantitatively analyze the conductivity in K 3 C The CC theory was developed for a superconductor which occupies the total half space.
In addition, the static and rf magnetic fields are parallel in our experiment, which is the standard case for the applicability of the CC theory. Albeit we cannot quantitatively consider the effect of the small particle size on the magnetic properties, we believe that neither the surface barriers also known as Bean-Livingstone barriers 58 nor the so-called geometrical barriers 59 affect considerably the applicability of the CC theory. The argument is that both types of barriers would affect the overall number of the vortices under the applied DC magnetic field or the B value where vortices appear but not the overall vortex dynamics under the application of the small AC magnetic field, which is the primary reason for the observed microwave absorption.
In Fig. The conductivity values are normalized by the normal state conductivity at the critical temperature. Two limiting cases are known. This approximates the measurement in the large K 3 C 60 single crystal. This approximates the K 3 C 60 sample of well divided small grains. We discuss that the experimental observations for the crystal and fine powder K 3 C 60 are explained well by these two regimes.
In the first case, when the rf field penetrates in the skin depth only known as the skin limit , the following equation holds between the microwave measurement parameters and the material quantities 28 :. The left panels in Fig. The calculation uses Eq. Clearly, the experimental data for the K 3 C 60 crystal match well the calculations.
Microwave Passive Microwave Device Applications of High-Temperature Superconductors tyruvyvizo.cf
Comparison of measured and calculated cavity loss and shift parameters in the skin left panels and penetration limit right panels. Calculation details are given in the text. Note that the calculated curves and the experimental data agree well for both sample types.
- Giant microwave absorption in fine powders of superconductors;
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We note that the experimental curves do not show such a rapid change as a function of temperature as the calculation. This may be related to the finite size and surface roughness of the single crystal sample. Second, we discuss the opposite limit, when the microwave field penetrates into the sample known as the penetration limit , the cavity measurables depend differently on the sample parameters.
It was shown 63 for a sphere with radius, a :. The right panels in Fig. We assumed that the sample consists of spheres with a uniform diameter, a. As shown in Fig. It means that a substantial microwave absorption occurs on the surface of the sample. This is further elaborated in the last part of the Supplementary Material.
In addition, Eq. A different particle shape or particle size distribution would allow for a different scaling factor for the loss and shift data which could also improve the fits. Although improved fits could be attained, we believe that the simplest model explains well the experimental observation of an enhanced microwave absorption.
In addition it allows to determine an effective pinning force constant, which is an important parameter to describe the electrodynamics of type-II superconductors. We demonstrated that moderate magnetic fields, which are small compared to the upper critical field, induces a large microwave absorption in fine powders of type II superconductors, like MgB 2 and K 3 C The effect is absent for samples containing larger grains or compacted powder pellets.
The Bardeen—Stephen model of flux-flow predicts that the real part of the AC conductivity can be enhanced in the microwave range, but this effect has not been observed.
Passive Microwave Device Applications of High-Temperature Superconductors
We analyze the conductivity using the Coffey—Clem theory which also accounts for vortex pinning effects. It is applied to calculate the microwave properties for two kinds of samples: when the electromagnetic field penetration is limited to the surface skin limit or when it fully penetrates into the fine grain samples penetration limit. A quantitative analysis for K 3 C 60 yields the vortex pinning force constant that can be hardly determined by other means. Our observation allowed us to explain long-standing microwave anomalies in superconductors 30 , 31 and it may lead to pertinent applications in microwave communication techniques.
K, SNN and This work P. The research was performed at the Ames Laboratory which is operated for the U. All authors contributed to writing of the manuscript. Electronic supplementary material. Supplementary information accompanies this paper at Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. National Center for Biotechnology Information , U.