SPIN EXCITATIONS AND PHONONS IN YBA2CU3O6- A STATUS-REPORT(X )

A review is made of recent developments in inelastic neutron scatterin g experiments on spin excitations and phonons in the high-temperature superconductor YBa2Cu3O6+x and its antiferromagnetic precursor YBa2Cu3 O6.2. These experiments include the detection of high-energy ''optical '' spin waves and the determination of the full spin Hamiltonian in YB a2Cu3O6.2, detailed investigations of the 40 meV magnetic resonance pe ak in the superconducting state of YBa2Cu3O7 and its precursors in und erdoped YBa2Cu3O6+x, and experiments on the effect of superconductivit y on phonon lifetimes in YBa2Cu3O7.