Systematic (63)Cu NQR and (89)Y NMR Study of Spin Dynamics in Y(1-z)Ca(z)Ba(2)Cu(3)O(y) Across Superconductor-Insulator Boundary

Abstract

We demonstrate that the spin dynamics in underdoped Y(1-z)Ca(z)Ba(2)Cu(3)O(y) for y=~6.0 exhibit qualitatively the same behavior to underdoped La(2-x)Sr(x)CuO(4) for an equal amount of hole concentration p=z/2=x<0.11. However,a spin-gap appears as more holes are doped into the CuO(2) plane by increasing the oxygen concentration to y=~6.5 for a fixed value of Ca concentration z. Our results also suggest that Ca doping causes disorder effects that enhance the low frequency spin fluctuations.

Accepted for publication in PRL, scheduled tentatively for the issue of: L 29Apr02