And NMR in superconductin oriented powder

B. Suh, F. Borsa, J. Sok, D. Torgeson, Ming Xu, Q. Xiong

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


(Formula presented) NMR measurements have been performed both in the normal and in the superconducting state for an oriented (Formula presented)(Formula presented) superconducting powder sample with (Formula presented)=96 K. The large anisotropic Knight shift of (Formula presented), (Formula presented)(Formula presented)=-0.15% at room temperature, is explained by the chemical shift related to the linear Hg-O(2) bonding configuration. Both (Formula presented)(Formula presented) and (Formula presented)(Formula presented) decrease below (Formula presented) and scale linearly with each other in the whole temperature range investigated. The (Formula presented) Knight shift (Formula presented)K slowly decreases with decreasing temperature on approaching (Formula presented) in the normal state, reflecting the decrease of the uniform spin susceptibility χ′(0,0) with lowering temperature. The (Formula presented) spin-echo decay can be fit by the product of a Gaussian component ((Formula presented)) and an exponential one ((Formula presented)). The Gaussian component (Formula presented) which is dominant above (Formula presented), is shown to be due mainly to an indirect nuclear interaction via the conduction electrons (holes) and is found to be directly proportional to the spin contribution (Formula presented)(Formula presented)) of the Knight shift. The exponential component (Formula presented) becomes dominant well below (Formula presented) and is ascribed to the effect of thermal motion of flux lines. The (Formula presented) nuclear spin-lattice relaxation rate (Formula presented) in the normal state shows a Korringa behavior well above (Formula presented) with ((Formula presented)T(Formula presented)=0.1 (Formula presented). Reduction of ((Formula presented)T(Formula presented) with decreasing temperature is observed starting about 10 K above (Formula presented) and is consistent with the decrease of χ′(0,0) in the normal state observed in K(T) and (Formula presented). (Formula presented)(Formula presented)(T) was extracted using the Korringa relation and below (Formula presented), is found to fit the d-wave pairing scheme with a superconducting gap parameter 2(Formula presented)=3.5(Formula presented). The d-wave pairing is also supported by the temperature dependence of (Formula presented) in the superconducting state. The (Formula presented) and (Formula presented) measurements have been performed in the normal state. In contrast to the Korringa behavior of (Formula presented) in the normal state, the preliminary results show the increase of the (Formula presented) ((Formula presented)T(Formula presented) with decreasing temperature, indicating the enhancement of the antiferromagnetic fluctuations of (Formula presented) moments common in the high-(Formula presented) cuprates. The reduction of (Formula presented) ((Formula presented)T(Formula presented) is observed starting above (Formula presented) and is compared with the decrease of (Formula presented), (Formula presented), and ((Formula presented)T(Formula presented) in the normal state. The (Formula presented) nuclear spin-spin relaxation (Formula presented) is found to follow an exponential decay in the normal state and to decrease with decreasing temperature similar to the (Formula presented) and (Formula presented).

Original languageEnglish
Pages (from-to)545-555
Number of pages11
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number1
StatePublished - 1996


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