Magnetic response of the J1-J2 spin Hamiltonian from classical Monte Carlo and Schwinger boson mean field theory

Magnetic susceptibilities at several potential ordering wave vectors (0,0), (\pi,0), and (\pi,\pi) are analyzed for the antiferromagnetic J1-J2 spin Hamiltonian by classical Monte Carlo and Schwinger boson mean field theories over the parameter range 0 \le 2J_2/J_1 \le 2. We find a nearly linear-T behavior of the uniform susceptibility that extends up to the temperature scale of J_1 within both calculation schemes when 2J_2/J_1 is sufficiently removed from the critical point 2J_2/J_1=1. The window of linear temperature dependence diminishes as the critical point is approached.