NMR measurement of the exchange coupling between Cu(2) atoms inYBa2Cu3

C. H. Pennington

¹

,

D. J. Durand

²

,

Charles P. Slichter

³

et al.

Abstract

The authors report the transverse NMR relaxation of chain [Cu(1)] and plane [Cu(2)] nuclei in a single crystal of YBazCu307s (T, =90 K) in the normal state. They demonstrate the ex-

Cu nuclear magnetic resonance study of charge and spin stripe order inLa1.875Ba0.125CuO4

“…In the limit where spin-flip processes dominate, it becomes pure exponential. An in-plane magnetic field makes spin flips important and causes an exponential relaxation 43 ; it therefore seems plausible that strong in-plane electron spin fluctuations have a similar effect. The relaxation thus becomes exponential when the spin fluctuations associated with charge stripe order occur below T CO .…”

“…Namely, the crossover from a Gaussian decay in the high-temperature phase to exponential below T CO we see here has been reported for other 214 cuprates 21 and YBCO 8 , but with somewhat incomplete explanations. It is known that the Gaussian decay in cuprates is generally caused by a strong CuCu transferred coupling 43,44 , and an unlike-spin coupling has been invoked to explain the crossover to exponential relaxation 21 . Yet such an explanation requires the existence of a significant fraction of wiped-out, quickly relaxing nuclei which cause the exponential echo decay of the observable nuclei.…”

“…The spin-spin decay curve will have a Gaussian shape if the transferred coupling between Cu nuclei is essentially static, i.e. when mutual spin flips are rare 43,44 . This happens in Cu NMR with the magnetic field perpendicular to the CuO 2 planes, and in NQR at elevated temperatures.…”

Magnetic phase transition at88KinNa0.5CoO2Pedrini1, Gavilano2, Felder3 et al. 2005Phys. Rev. B131140View full textAdd to dashboardCite

“…A value b = 1 is attributed to indirect coupling between the nuclear spin at the different Na nuclei (for example, electron-mediated spin-spin interaction [30,31]), as opposed to direct scalar or dipolar interactions which yield b = 1. For example, a value b = 2 was predicted and observed for the 63,65 Cu NMR spin-echo decay in high-temperature superconductors [32,33]. The exact value of b depends on the details of the indirect coupling mechanism.…”

( Sr / Ca ) 14 Cu 24 O 41 spin ladders studied by NMR under pressure

“…The 1/T 2G Gaussian rate in copper oxides is related to the magnetic correlation length ξ of the spin fluctuations, [55,56]. Furthermore, the actual relationship between ξ and T 2G is determined by the dimensionality of the materials.…”