Title

Possible Ordering of Ru and Cu in the Charge-Reservoir of Magneto-Superconductor RuSr₂GdCu₂O₈ (Ru-1212): Magnetic, Transport, and TEM Microstructural Studies

Abstract

Magnetization vs temperature behavior of RuSr 2GdCu 2O 8-δ (Ru-1212) measured in an field of 5 Oe, shows a clear branching of zero-field-cooled (ZFC) and field-cooled (FC) curves around 140 K, a cusp at 135 K, and a diamagnetic transition around 20 K (in the ZFC branch). The cusp at 135 K is due to the antiferromagnetic ordering of the Ru moments. The magnetization-field isotherms, below 50 K, show a nonlinear contribution from a ferromagnetic component. The resistance vs temperature behavior of the compound, in applied fields of 0, 3, and 7 T, confirms that the sample is superconducting at around 20 K. The superconducting transition exhibits field broadening of a type different than that known for conventional high T c superconductors. The magnetoresistance (MR) is negative above the Ru magnetic ordering temperature of 135 K, while below this temperature, MR displays a positive peak in low fields and becomes negative in higher fields. A maximum of 2% is observed for the negative MR value at the Ru magnetic ordering temperature. An electron diffraction pattern obtained for this Ru-1212 sample shows two types of superstructure; one with a weak spot at the center of the a-b rectangle and the other only along the b direction. It is possible that either Ru/Cu or Ru 4+/Ru 5+ ordering of 2b periodicity takes place along the b direction. © 2002 American Institute of Physics.

Department(s)

Physics

Second Department

Chemistry

International Standard Serial Number (ISSN)

0021-8979

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2002 American Institute of Physics (AIP), All rights reserved.

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