Spin-wave dispersion and transition temperature in the cuprate antiferromagnet La2CuO4

Abstract

We have studied the spin-wave dispersion at low temperatures and the transition temperature (TN) of the spin-12 antiferromagnet and high-TC parent La2CuO4. The values of the in-plane exchange parameters (including first, second, and third nearest neighbors) are determined by an accurate fit to the recently experimentally observed in-plane spin-wave spectrum, obtained by the high-resolution inelastic neutron scattering performed on La2CuO4 [Phys. Rev. Lett. 86, 5377 (2001)]. The analysis of the Néel temperature shows that the in-plane spin anisotropy (η) is much more significant than the three dimensionality, since TN of the three-dimensional (3D)-antiferromagnet depends rather weakly on the value of the interlayer coupling (λ⊥). We obtain that the Néel temperature of the 3D-antiferromagnet varies only weakly within the very wide interval of λ⊥ and the Néel temperature of the anisotropic 2D (η≠0, λ⊥=0) antiferromagnet does not differ from the 3D value for the same η. These conclusions are valid for both tetragonal and orthorhombic structures. However, η dependence of TN is essentially different: for η=0, TN of the tetragonal structure becomes 0, while TN of the orthorhombic structure remains finite. These results are valid within the frame of the Tyablikov approximation.

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