Thermodynamic Properties of the Square-Lattice Heisenberg Antiferromagnet

Abstract

The thermodynamic properties of the square lattice Heisenberg antiferromagnet are investigated on the basis of the study of spin-wave excitation in previous paper [T. Aoki: J. Phys. Soc. Jpn. 59 (1990) 706]. The susceptibility and specific heat are calculated and compared with the results from other studies. The calculation of correlation function in the previous paper is reexamied and partly corrected. From this the existence of long-range order is shown and its amplitude is estimated. The agreement with numerical study is good. Our formula for inverse correlation length is compared with the recent neutron-scattering data of La₂CuO₄. If we choose J=1100 K, good agreement is obtained at low temperatures.