Absorption at radio frequencies in superconducting Y₁Ba₂Cu₃O_y

Authors

Stephen Ducharme, University of Nebraska - LincolnFollow
R. Durny, Department of Physics, University of Utah - Salt Lake City
J. Hautala, Department of Physics, University of Utah - Salt Lake City
D.J. Zheng, Department of Physics, University of Utah - Salt Lake City
P.C. Taylor, Department of Physics, University of Utah - Salt Lake City
O.G. Symko, Department of Physics, University of Utah - Salt Lake City
S. Kulkarni, Ceramatec, Inc., Salt Lake City, Utah

Date of this Version

August 1989

Comments

Published by American Institute of Physics. J. Applied Physics 66, 1252 (1989). ©1989 American Institute of Physics. Permission to use. Journal home page = http://jap.aip.org/jap/.

Abstract

The large magnetic-field-dependent ac absorption in superconducting Y₁Ba₂Cu₃O_y ceramics and powders decreases slowly with increasing frequency in the range 2–16 MHz. The magnetic-field-dependent ac absorption is observed below T_c in superconducting Y₁Ba₂Cu₃O_y ceramics, powders and twinned crystals and in (La,Sr)₂ CuO₂ and BaPb_0.75 Bi_0.25 CuO₃ powders and appears to contain distinct contributions from trapped flux and/or intragrain tunnel junctions and from ordinary superconductor surface impedance. The contribution from trapped flux and/or intragrain tunnel junctions is important in dc magnetic fields of up to approximately 20 G at all temperatures below T_c. There is an identifiable modulated ac absorption which changes slowly over more than 12 kG at low temperatures and which we propose is primarily caused by the ac surface impedance with possible contributions from the critical state. A twinned crystal of Y₁Ba₂Cu₃O_y exhibits the same ac absorption except that it has an anisotropic dependence on the applied dc magnetic field.