Abstract
NQR and relaxation measurements in , for 0⩽x⩽0.11 and in the temperature range ⩽T⩽900 K, are presented. The results are used to derive insights into the correlated spin dynamics in the paramagnetic phase of the S= two-dimensional (2D) Heisenberg (H) antiferromagnets (AF), and into the disorder effects associated with the spin vacancy due to (S=0) for substitution. In particular, by using scaling arguments for the static generalized susceptibility, χ(q-→,0), and for the decay rate, , of the normal excitations, and are related to the in-plane correlation length (x,T) and its dependence on temperature and Zn doping, x, is extracted. The experimental findings are analyzed in light of the quantum critical and renormalized classical behaviors for predicted by recent theories for S=1/2 HAF on square lattices. It is shown that up to T≃900 K, is consistent with the assumption of a renormalized classical regime, in agreement with recent neutron scattering results and at variance with previous interpretations of the NQR data. It is discussed how Zn affects through the modification in the spin stiffness and comparison with the disorder induced by itinerant extra holes is made.
DOI:https://doi.org/10.1103/PhysRevB.55.3734
©1997 American Physical Society