Inelastic Neutron Scattering studies of pure and Mo doped VO$_{2}$

For the last half-century~VO$_{2}$ has been viewed as an~archetypal system for studying~the~metal-insulator~transition (MIT). Moreover, there is currently intense interest in this material arising from its promising use in fast energy efficient electronic devices.~ There are key unresolved issues connected with the origin of ~the MIT, including the role of magnetism arising from the S$=$1/2 V$^{4+}$ ions.~ It is known that below 340 K in undoped VO$_{2}$ the V ions form structural dimers in the insulating M1 monoclinic phase.~ Here we report the results of new inelastic neutron scattering measurements of VO$_{2}$ and V$_{0.75}$Mo$_{0.25}$O$_{2}$. Using the~SEQUOIA chopper spectrometer at the SNS~possible lattice and magnetic excitations for energies up to 600 meV were investigated. We discuss the results in the context of current ideas concerning the MIT in VO$_{2}$.