Spin-wave expansion of the staggered magnetization of a square-lattice Heisenberg antiferromagnet at T=0

Spin-wave expansion is used to compute the staggered magnetization of the square-lattice Heisenberg antiferromagnet at T=0 to order O(1/S${)}^2$. It is found that the staggered magnetization, ${\mathit{M}}^{\mathrm{°}}$, is given by ${\mathit{M}}^{\mathrm{°}}$=S-0.19660×${\mathit{S}}^0$+0×${\mathit{S}}^{\mathrm{-}1}$-0.00068×${\mathit{S}}^{\mathrm{-}2}$ +O(${\mathit{S}}^{\mathrm{-}3}$). The result strengthens the belief that spin-wave expansion, at T=0, is a useful asymptotic expansion that agrees exceptionally well with recent Monte Carlo and series-expansion estimates of the staggered magnetization.