Non-magnetic defect in the two-dimensional s=1/2 Heisenberg antiferromagnet with honeycomb lattice

We study the effect of a non-magnetic defect on the properties of the s = 1/2 two-dimensional Heisenberg antiferrornagnet with honeycomb lattice at T = 0. A modified Oguchi method is used to calculate the moment reduction and nearest-neighbour correlations for clusters of up to 13 spins embedded within the molecular field of the remainder of the lattice. A single non-magnetic defect is introduced to study the effect of magnetic dilution on the moment reduction. To the accuracy of the calculations there is no change in moment reduction for small dilutions. The dependence of the moment on dilution is further modelled by reducing the molecular field with magnetic dilution so that the approach to quantum criticality is a co-operative phenomenon. (C) 2003 Elsevier B.V. All rights reserved.