Antiferromagnetism of the t-J Model in the Slave Boson Mean Field Approximation

The antiferromagnetic state of the t - J model present in the low doping region in high- T c cuprates is studied in the mean field approximation based on the slave boson framework. It is found that there is a phase transition between localized and itinerant antiferromagnetism depending on the doping rate; the Néel temperature is that of localized spins, i.e., without the Fermi surface of spinons, in the region of very low doping, whereas above critical doping, the onset temperature of the coherent motion of spinons and holons is higher than the Néel temperature. The staggered magnetic moment near absolute zero decreases with doping due to the increasing degree of itineracy, which is consistent with various experiments.