RESONANT NEUTRON-SCATTERING FROM YBA2CU3O7

We have developed a new scattering geometry for magnetic neutron scatt ering experiments on YBa2Cu3O7 in which the phonon background around q similar to (pi/alpha,pi/alpha), h omega similar to 40meV is significa ntly reduced. We use this new approach to study the previously detecte d, sharp magnetic excitation at similar to 40meV in the superconductin g state in detail. The excitation does not shift substantially in ener gy up to at least 75K (similar to 0.8T(c)). Polarized neutron scatteri ng experiments (horizontal minus vertical field) confirm the magnetic origin of the 40meV excitation and put stringent limits on the magneti c scattering intensity in the normal stale.