Temperature dependence of sublattice magnetization in quasi-two-dimensional S=1/2 cuprate antiferromagnets: Green’s function approach

The study of temperature dependence of the sublattice magnetization in the quasi-two-dimensional S=1/2 cuprate antiferromagnets was inspired by the existing experimental evidence concerning sublattice magnetization temperature dependence, both in the vicinity of absolute zero for the high-T_C parent compound La₂CuO₄ and in the whole temperature region from absolute zero to the Néel temperature (T_N) for La₂CuO₄ and YBa₂Cu₃O_6.15. Using the spin Green’s functions method for the quantum Heisenberg antiferromagnetic model, we obtain the results which show excellent agreement with the experimental data, proving that in the wide temperature region (from 0 to T_N), this method is more appropriate than the harmonic spin-wave theory and Schwinger-boson mean-field theory.