1993 年 62 巻 9 号 p. 3062-3070
The Néel and collinear order parameters of the J1-J2 model are calculated by the quantum Monte Carlo simulation with the reweighting method. Systems of sizes N=4×4, 4×8 and 8×8 are treated. The thermodynamic quantities obtained by the size extrapolation suggest that the Néel order remains finite for α≤0.4 and vanishes for α>0.6, where α is defined by J2⁄J1, and that the collinear order remains for α≥0.7 and vanishes for α<0.6. The present result is consistent with the result of the modified spin-wave calculation, conflicting with that of the naive spin-wave theory.
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