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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 Kuzian^1,2, Satoshi Nishimoto¹, Jiri Malek^1,3, 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.