Eur. Phys. J. B 3, 333-340 (1998)
https://doi.org/10.1007/s100510050319

Explanation of the Cu spin-wave excitation gap in NdCuO

Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

Corresponding author: ^a pyttlik@physik.tu-dresden.de

Received: 13 August 1997
Revised: 4 December 1997
Accepted: 11 December 1997
Published online: 15 June 1998

Abstract

By use of a mean-field approach the spin-wave dispersion of the Cu degrees of freedom in the undoped high-T _C material Nd₂CuO₄ is investigated. The experimentally observed sharp decrease of the Cu spin-wave gap with increasing temperature in the range is explained by a paramagnetic-like susceptibility of the Nd spins which couple to the Cu subsystem. The degeneracy of the "in-plane" and "out-of-plane" polarized Cu spin-wave branches is shown to be lifted by the uniaxial anisotropy of the Cu-Cu nearest-neighbor interaction.