Spin fluctuations in a metallic antiferromagnet

Abstract

The magnon energy and amplitude renormalization due to intraband particle-hole excitations are studied in a metallic antiferromagnet. The change in sign of the intraband contribution with $\omega$ results in significant differences between static and dynamical behaviours. For electron doping, while the coherent magnon peak looses spectral weight and is shifted to higher energy with doping, the low-energy incoherent part becomes increasingly prominent as it narrows in width and shifts to lower energy. Implications for spin dynamics in the electron-doped cuprate $\mathrm{N}{\mathrm{d}}_{2-\mathrm{x}}\mathrm{C}{\mathrm{e}}_{\mathrm{x}}\mathrm{Cu}{\mathrm{O}}_4$ are discussed. Due to an exact cancellation of two logarithmically divergent spin-fluctuation processes, the AF order parameter is unaffected to leading order. For hole doping, short wavelength transverse perturbations ($q>q^{\ast }\sim \sqrt{x}$) are found to be stable, implying short-range AF order with a spin correlation length $\xi /a\sim 1/\sqrt{x}$.

8 pages, 13 figures