Giant microwave absorption in fine powders of superconductors

Enhanced microwave absorption, larger than that in the normal state, is observed in fine grains of type-II superconductors (MgB 2 and K 3 C 60 ) for magnetic fields as small as a few % of the upper critical field. The effect is predicted by the theory of vortex motion in type-II superconductors, how...

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Published in:Scientific reports Vol. 8; no. 1; pp. 11480 - 9
Main Authors: Csősz, G., Márkus, B. G., Jánossy, A., Nemes, N. M., Murányi, F., Klupp, G., Kamarás, K., Kogan, V. G., Bud’ko, S. L., Canfield, P. C., Simon, F.
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 31.07.2018
Nature Publishing Group
Subjects:
639/766/119
639/766/119/1003
Absorption
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Humanities and Social Sciences
Magnetic fields
multidisciplinary
Science
Science (multidisciplinary)
Skin
Superconductors
ISSN:2045-2322, 2045-2322
Online Access:Get full text
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Summary:Enhanced microwave absorption, larger than that in the normal state, is observed in fine grains of type-II superconductors (MgB 2 and K 3 C 60 ) for magnetic fields as small as a few % of the upper critical field. The effect is predicted by the theory of vortex motion in type-II superconductors, however its direct observation has been elusive due to skin-depth limitations; conventional microwave absorption studies employ larger samples where the microwave magnetic field exclusion significantly lowers the absorption. We show that the enhancement is observable in grains smaller than the penetration depth. A quantitative analysis on K 3 C 60 in the framework of the Coffey–Clem (CC) theory explains well the temperature dependence of the microwave absorption and also allows to determine the vortex pinning force constant.
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USDOE
AC02-07CH11358
IS-J-9647
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-29750-7