Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 40: Correlated Electrons: Low-dimensional Systems - Materials 3
TT 40.3: Vortrag
Donnerstag, 29. März 2012, 15:30–15:45, H 0104
Ca2Y2Cu5O10: the first authentic frustrated quasi-1D ferromagnet and a particular rehabilitation of spin wave theory based analysis — •Stefan-Ludwig Drechsler1, Roman Kuzian1,2, Satoshi Nishimoto1, Jiri Malek1,3, Jeroen van den Brink1, Miriam Schmitt4, Helge Rosner4, Masaaki Matsuda5, Kunihiko Oka6, Hirotaka Yamaguchi6, and Toshimitsu Ito6 — 1IFW-Dresden, ITF, D01171 Dresden, Germany — 2Inst. f. Problems of Material Sciences, NASU, Kiev, Ukraine — 3Inst. of Physics, ASCR, Prague, Czech Republic — 4MPI-CPFS, Dresden, Germany — 5Quantum Cond. Division, Oak Ridge National Lab., Oak Ridge, USA — 6AIST, Tsukuba, Ibaraki, Japan
We reexamine the magnetic excitations (ME) for Ca2Y2Cu5O10 with edge-shared CuO2 chains (ESC). For this aim we report inelastic neutron scattering data and present the ME dispersion along Q=(H,0,1.5), unaffected by the main interchain couplings. This allows a precise extraction of the inchain couplings (IC) J1 ≈−170 K, J2 ≈ 32 K. Their ratio α=|J2/J1|≈0.19 indicates an exceptional position in the ESC family: close to the critical point (CP) of the J1-J2 spin model α c=1/4, but on the ferromagnetic (FM) side of its phase diagram. The obtained J’s agree with the results obtained for a realistic 5-band extended Hubbard pd model and L(S)DA+U calculations. We predict Zhang-Rice singlet features in RIXS, EELS and optics visible at 300 K for sizable frustration only. This is the signature of a frustrated FM near a CP. The weak IC determine the predicted saturation field of 65 T and J1 gives the width of the ME dispersion.