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Nuclear Relaxation and Knight Shift Studies of Copper in YBa 2 Cu 3 O 7- y

1988; Physical Society of Japan; Volume: 57; Issue: 1 Linguagem: Inglês

10.1143/jpsj.57.30

1347-4073

Yoshio Kitaoka, Shigeru Hiramatsu, Takayuki Kondo, Kei Asayama,

Magnetic properties of thin films

The nuclear relaxation rate 1/ T 1 and the Knight shift have been studied for boththe Cu–O plane and chain sites by Cu nuclear quadrupole (NQR) and magnetic resonance (NMR) techniques. Below T c =92 K, 1/ T 1 for the plane site decreases markedly without the enhancement just below T c characteristic for the BCS superconductor, and the Knight shift also shows a more rapid reduction than the BCS prediction, giving evidence of a dominant singlet pairing. In contrast, 1/ T 1 for the chain site shows a weak temperature dependence below T c . This difference of the 1/ T 1 behavior for the plane and chain Cu sites is attributed to the difference of the relaxation processes, i.e., the magnetic and quadrupole relaxation processes, respectively. From both the behaviors of 1/ T and the Knight shift at the plane site, it is pointed out that the Cooper pair may be of a d-type formed by a strong coupling with a large energy gap.