MAGNETIC EXCITATIONS IN THE SPIN LADDER SYSTEM (VO)(2)P2O7

We present the results of elastic and inelastic neutron scattering mea surements made on a powder sample of the spin-ladder compound (VO)(2)P 2O7. The elastic scattering measurements made at a temperature of 10 K showed no magnetic structure, consistent with a singlet ground state. The inelastic measurements, also at 10 K, revealed three magnetic mod es at 3.5, 6.0, and 14 meV. Theoretical treatments of spin ladder mode ls point to an identification of the 3.5 meV mode as the minimum in th e one-magnon dispersion, and the 14 meV mode as the local minimum in t he associated two-magnon continuum. However, we have been unable to ex plain the scattering at 6.0 meV using existing theories of spin ladder s. (C) 1997 American Institute of Physics.