Microwave performance of high-density bulk MgB[sub 2]

Findikoglu, A. T.; Serquis, A.; Civale, L.; Liao, X. Z.; Zhu, Y. T.; Hawley, M. E.; Mueller, F. M.; Nesterenko, V. F.; Gu, Y.
July 2003
Applied Physics Letters;7/7/2003, Vol. 83 Issue 1, p108
Academic Journal
We have performed microwave measurements on superconducting hot-isostatically pressed (HIPed) bulk MgB[SUB2] using a parallel-plate resonator technique. The high density and strength of the HIPed material allowed preparation of samples with mirror-like surfaces for microwave measurements. The microwave effective surface resistance R[SUBs] decreased by about 40% at 20 K when the root-mean-square surface roughness was reduced from 220 to 110 nm through surface polishing and ion milling. The R[SUBs] was independent of surface microwave magnetic field at least up to 4 Oe and below 30 K. We attribute this behavior, and the overall low R[SUBs] (∼0.8 mohm&; at 10 GHz and 20 K), to the high density of our samples and the absence of weak links between grains.


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