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, M, is given by M = S -0.19660 x S0 + 0 x S-1 -0.00068 x S-2 + O(S-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.