Table of Contents
ISRN Condensed Matter Physics
Volume 2011 (2011), Article ID 929713, 3 pages
http://dx.doi.org/10.5402/2011/929713
Research Article

Paramagnetic Resonance as a Probe of the Spin Gap in Normal State of H g . πŸ• πŸ• P b . πŸ‘ πŸ‘ B a 𝟐 C a 𝟐 C u πŸ‘ O πŸ– + π‘₯ Superconductor

Department of Physics, Hunter College, CUNY, 695 Park Avenue, New York, NY 10065, USA

Received 30 August 2011; Accepted 26 September 2011

Academic Editors: S. Balamurugan and J. Bok

Copyright © 2011 Frank J. Owens. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

It is shown that electron paramagnetic resonance (EPR) can be used to observe the spin gap in copper oxide superconductors. The electron paramagnetic resonance spectra of the Cu2+ ion in underdoped H g . 7 7 P b . 3 3 B a 2 C a 2 C u 3 O 8 + π‘₯ show a pronounced decrease in intensity in the normal state as the temperature is lowered to 133 K, the superconducting transition temperature of the material. The decrease is attributed to a pairing of the Cu2+   𝑠 = 1 / 2 spins to form a spin gap. A spin gap of 0.0533 eV is estimated from the data which is in order of magnitude agreement with values obtained from NMR measurements.