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A modified spin-wave theory for the Heisenberg antiferromagnet (scrH=J) is formulated under the assumption of zero sublattice magnetization in the same way with the Heisenberg ferromagnet. This theory gives self-consistent equations which are equivalent to those of Auerbach and Arovas, but in our theory the factor of (3/2 in the correlation function does not appear. This theory reproduces the main results of traditional spin-wave theory, as well as those of renormalization-group theory, in a unified picture. For the square lattice at low temperature the susceptibility behaves as a+bT and the correlation length as (c/T) exp (d/T). This correlation length coincides very well with experimental results of La₂CuO₄ if we choose J=900 K. Calculation of self-consistent equations is done for the S= (1/2 system and compared with the result of exact diagonalization of a 44 system and high-temperature expansion. The quantitative agreement is surprisingly good, especially at T0. 6J. . AE
Minoru Takahashi (Tue,) studied this question.