In a recent paper \cite{Radu}, Radu \textit{et al.} report experimental results they claim to support Bose-Einstein condensation (BEC) of magnons in Cs2CuCl4. It is true that an experimentally measured critical power law scaling exponent in agreement with the BEC universality class would support the realization of a BEC in magnetic systems that order as a canted antiferromagnet. It can be shown, however, that the claim of Radu {\it et al.} is overstated in this instance, because their determination of the critical exponent ϕ relies on a model-dependent theoretical approximation to the critical field Hc1 for which the associated errors are neglected. We show that when these errors are included, the uncertainty in the obtained exponent is so large that the available experimental data cannot be used to differentiate between contending universality classes.
@article{arxiv.cond-mat/0512193,
title = {On the Bose-Einstein Condensation of Magnons in Cs2CuCl4},
author = {S. E. Sebastian and V. S. Zapf and N. Harrison and C. D. Batista and P. A. Sharma and M. Jaime and I. R. Fisher and A. Lacerda},
journal= {arXiv preprint arXiv:cond-mat/0512193},
year = {2011}
}