title: In-gap spin excitations and finite triplet lifetimes in the dilute singlet ground state system SrCu(2-x)Mgx(BO3)2.
abstract: High resolution neutron scattering measurements on a single crystal of SrCu(2-x)Mgx(BO3)2 with x approximately 0.05 reveal the presence of new spin excitations within the gap of this quasi-two-dimensional, singlet ground state system. The application of a magnetic field induces Zeeman-split states associated with S=1/2 unpaired spins which are antiferromagnetically correlated with the bulk singlet. Substantial broadening of both the one- and two-triplet excitations in the doped single crystal is observed, as compared with pure SrCu2(BO3)2. Theoretical calculations using a variational algorithm and a single quenched magnetic vacancy on an infinite lattice are shown to qualitatively account for these effects.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Haravifard
authors.forename: S R
authors.initials: SR
authors.lastname: Dunsiger
authors.forename: S
authors.initials: S
authors.lastname: El Shawish
authors.forename: B D
authors.initials: BD
authors.lastname: Gaulin
authors.forename: H A
authors.initials: HA
authors.lastname: Dabkowska
authors.forename: M T F
authors.initials: MT
authors.lastname: Telling
authors.forename: T G
authors.initials: TG
authors.lastname: Perring
authors.forename: J
authors.initials: J
authors.lastname: Bonca