^63 Cu NQR and NMR of YBa _2 Cu _3 O _6+x at Elevated Temperatures

Session Q09 - HTSC: STRUCTURES AND DEFECTS
Mixed session, Friday morning, March 24, 8:00
Ballroom A5, San Jose Convention Center

[Q09.06] ^63 Cu NQR and NMR of YBa _2 Cu _3 O _6+x at Elevated Temperatures

S.P. Klein$^*$,W.W. Warren, Jr.$^*$ (Department of Physics, O.S.U.),R.-P. Wang,A.W. Sleight (Department of Chemistry, O.S.U.)

We have explored the evolution of the ^63 Cu nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) spectra over a temperature range from room temperature to 200 ^\circ C in samples close to the composition YBa _2 Cu _3 O _7 . For both the Cu(1) and Cu(2) sites, there is an unexpected and abrupt loss of signal intensity over a range of about 75 ^\circ C\@. The onset of signal loss occurs at a higher temperature in samples of higher quality as indicated by their NQR spectra. The effect of elevated temperatures on the quadrupolar broadened central (\Delta m = \pm 1/2) of the nuclear magnetic resonance (NMR) spectrum is very small. The relationship of these effects to oxygen motion and sample quality will be discussed.

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\noindent ^* Partially supported by NSF grant DMR 93-05780.

Part Q of program listing