Inelastic neutron scattering investigation of magnetic excitations in the spin-Peierls ground state of (TMTTF)2PF6(TMTTF)2PF6

We present the first inelastic neutron scattering investigation of magnetic excitations in a one- dimensional (1D) organic conductor. This experiment is conducted in the spin-Peierls (SP) ground state of (TMTTF)2PF6(TMTTF)2PF6. The study, performed with a 98% deuterated powder, reveals the double gap structure of magnetic excitations of the SP chain. These responses, as well as the observation of a higher energy mode, occur at energies consistent with microscopic coupling deduced from magnetic measurements performed on the same sample.