Berlin 2018 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 6: Quantum Magnets and Molecular Magnets (joint session TT/MA)
TT 6.6: Vortrag
Montag, 12. März 2018, 10:45–11:00, H 3010
Highly dispersive magnons with spin-gap like features in the frustrated ferromagnetic chain system Ca2Y2Cu5O10 by inelastic neutron scattering — M. Matsuda1, J. Ma1, V.O. Garlea1, T. Ito2, H. Yamaguchi2, K. Oka2, •S.-L. Drechsler3, R. Yadav3, L. Hozoi3, H. Rosner4, R. Schumann5, R. Kuzian6, and S Nishimoto3,5 — 1Quantum Matter Division, Oak Ridge, NRL, USA — 2Natiomal Institute of AIST, Tsukuba, Japan — 3IFW-Dresden, Germany — 4MPI-CPfS, Dresden, Germany — 5TU Dresden, Germany — 6Inst. f. Problems of Material Science, Kiev, Ukraine
We report an inelastic neutron scattering study including its theoretical description for Ca2Y2Cu5O10 and map out the full large magnetic dispersion relation extending up to 53 meV. A doubly frustrated linear Heisenberg-type spin chain model with two inchain and two diagonal antiferromagnetic (AFM) interchain couplings (IC) analyzed within linear spin-wave theory reproduces well the observed strong dispersion in chain direction and q weak one perpendicularly. The large dispersion leads to a record value of the NN intrachain coupling ∣ J1∣ ≈ 280 K which points to a large direct FM Cu-O coupling Kpd value slightly above 100 meV. Our J1-value resolves an old puzzle of FM inchain ordering vs. an improper AFM pseudo Curie-Weiss (CW) behavior for χ(T). It yields a true FM CW-regime above 1500 K, only. The observed "gaps" at 11.5 and 28 meV stem from an interaction with a phonon mode and the synenergetic disorder influence on the CuO2 chains by the incommensurate alternating cationic YCa-chains distorting the O positions and a specific quantum effect from the AFM IC, respectively.