Phonon and Magnetic Neutron Scattering at 41 Mev in YBa₂Cu₃O₇

We report inelastic neutron scattering measurements at excitation energies Latin small letter h with strokeω~41 meV in YBa2Cu3O7. We separate magnetic and phonon contributions to the scattering cross section by a detailed analysis of the momentum dependence of the scattered intensity. The previously reported broad peak around q=(π/a,π/a) in the normal state can be entirely accounted for by a phonon which primarily involves vibrations of the in-plane oxygen. Magnetic scattering centered around 41 meV and q=(π/a,π/a) appears in the superconducting state only. Theoretical implications of these findings are discussed

Resonant Neutron Scattering from YBa₂Cu₃O₇

We have developed a new scattering geometry for magnetic neutron scattering experiments on YBa2Cu3O7 in which the phonon background around q ~ ( π a, π a), ω ~ 40meV is significantly reduced. We use this new approach to study the previously detected sharp magnetic excitation at ~ 40meV in the superconducting state in detail. The excitation does not shift substantially in energy up to at least 75K. (~0.8Tc). Polarized neutron scattering experiments (horizontal minus vertical field) confirm the magnetic origin of the 40meV excitation and put stringent limits on the magnetic scattering intensity in the normal state