ON THE THEORY OF THE 2-DIMENSIONAL HEISENBERG-ANTIFERROMAGNET WITH FRUSTRATION ON A SQUARE LATTICE

The two-dimentional frustrated S=1/2 Heisenberg antiferromagnet is studied with a Green function decoupling method in a spherical approach. The second order phase transition from long-range order stale to spin liquid state is found at lambda=J(2)/J(1)=0.12 where J(1),J(2) describe the nearest and next nearest neighbors antiferromagnetic interaction. The temperature dependence of correlation functions C-rho, spin spectrum gap and uniform susceptibility chi is presented before and after transition. The dependence of chi on lambda and T turns out close to the dependence of chi on doping parameter x and T in high-T-c superconductors. The discussion points out the importance of detailed dependence of C-rho on T and lambda for the hole spectrum of doped CuO2 plane.