A quasi-2D nonlinear spin wave theory for the insulating undoped cuprates

Abstract

We propose a nonlinear spin wave theory of anisotropic 3D (quasi-2D) quantum Heisenberg antiferromagnets, which is equivalent to or reduces to known spin wave theories of isotropy parameter δ takes the values 0 or 1, respectively. With δ increasing from zero also the Néel temperature T N increases from zero. Applied to the antiferromagnetism of the layer-like cuprate La 2CuO 4 it describes quite satisfactorily the existing experimental data of the Néel temperature, correlation length, and staggered magnetization of the material if J = 1034 K and δ = 4×10 −5.