Static spin susceptibility in the <Emphasis Type="Italic">t</Emphasis>-<Emphasis Type="Italic">J</Emphasis> model

Based on the equation-of-motion method for the relaxation function expressed in terms of Hubbard operators, we evaluate the static spin susceptibility and correlation functions in the two-dimensional t-J model. We show that at zero temperature, a long-range antiferromagnetic order exists in the lattice for the hole concentration δ < δ_c ≃ 0.018. The calculated dependences of the spin susceptibility and correlation length on the temperature and hole concentration agree qualitatively with the experiment. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 3, pp. 538–550, September, 2007.