An Overall Energy Spectrum of Magnetic Fluctuations in the Superconducting La_1.85Sr_0.15CuO₄

Abstract

High-energy pulsed neutron inelastic scattering experiments have been performed using single crystals of La 1.85 Sr 0.15 CuO 4 to study magnetic fluctuations in the superconducting phase. A peak centered at the reciprocal point (π,π) is well defined below around 120 meV and rapidly damped beyond this energy. However, the \lq\lqbackground-subtracted” scattering intensities indicate that magnetic signals remain up to around 300 meV. These data combined with the results obtained by triple-axis neutron scattering experiments provide the first overall energy spectrum of the dynamical susceptibility in La 1.85 Sr 0.15 CuO 4 . The obtained spectrum is much wider than that of YBa 2 Cu 3 O 7- d ( d ∼0).