We present a Monte Carlo study of the correlation length ξ of randomly diluted antiferromagnetic Heisenberg ladders, composed of two spin--1/2 chains. For weak and intermediate inter--chain couplings, J⊥/J≤1, we find an enhancement of correlations that is strongest for a fraction z∗≈J⊥/(8J) of dilutants. We are able to access the experimentally relevant low--temperature regime, T/J≈1/500, and find that the recently inferred N\'eel temperature of Sr(Cu1−zZnz)2O3 corresponds to a curve of constant correlation length ξ≈18 of the single diluted ladder with J⊥/J\alt1/2. The primary reason for the N\'eel ordering is argued to be a strong enhancement of two--dimensional correlations due to a Cu--Sr--Cu exchange coupling of ≈10meV in the stacking direction of the ladders.
@article{arxiv.cond-mat/9803064,
title = {Correlations and N\'eel Order of Randomly Diluted Quantum Spin Ladders},
author = {M. Greven and R. J. Birgeneau},
journal= {arXiv preprint arXiv:cond-mat/9803064},
year = {2009}
}