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Title: 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 3C 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. In conclusion, a quantitative analysis on K 3C 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.
Authors:
 [1] ;  [1] ;  [1] ; ORCiD logo [2] ;  [3] ;  [4] ; ORCiD logo [4] ;  [5] ;  [5] ;  [5] ;  [1]
  1. Budapest Univ. of Technology and Economics and MTA-BME Lendulet Spintronics Research Group (PROSPIN), Budapest (Hungary)
  2. Dept. de Fisica de Materiales Univ. Complutense de Madrid, Madrid (Spain)
  3. Mettler-Toledo GmbH, Nanikon (Switzerland)
  4. Hungarian Academy of Sciences, Budapest (Hungary)
  5. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9647
Journal ID: ISSN 2045-2322; PII: 29750
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1464489