Magnetic dynamics of La2CuO4 and La2−xBaxCuO4

Abstract

High-energy inelastic neutron scattering is used to resolve spin waves in ${\mathrm{La}}_2$ ${\mathrm{CuO}}_4$. The corresponding long-wavelength velocity is 0.85±0.03 eV Å, well above previous bounds set by thermal neutron scattering. Within experimental error, conventional spin-wave theory gives an excellent description of the magnetic dynamics for momentum and energy transfers below 0.15 A${̊}^{\mathrm{-}1}$ and 0.1 eV, respectively. Doping with Ba changes the magnetic dynamics; the data indicate a combination of spin-wave softening and damping effects.