High energy magnetic excitations from the edge-sharing CuO2 chains in Ca2Y2Cu5O10

Ca2Y2Cu5O10 is a quasi-one-dimensional magnet, which consists of the ferromagnetic edge-sharing CuO2 chains. It was previously reported from neutron inelastic scattering experiments in Ca2Y2Cu5O10 up to ∼14 meV that in the magnetically ordered state there is an anomalous broadening of spin-wave excitations along the chain, which is caused mainly by the antiferromagnetic interchain interactions [M. Matsuda et al.: Phys. Rev. B 63 (2001) 180403 (R)]. In this study we extended an energy range of the measurement up to ∼25meV. The experimental result suggests that there exist two excitation modes, which is consistent with a theoretical result qualitatively. One mode corresponds to the relatively sharp spin-wave excitations, which broaden with increasing qchain and disappear around qchain ∼0.2 r.l.u. and ω∼10meV. Another one corresponds to the very broad excitations apparent at qchain∼0.2-0.3 r.l.u. and ω ∼ 12-25 meV. (author)