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TT: Tiefe Temperaturen

TT 19: Correlated Electrons: Low-dimensional Materials

TT 19.8: Talk

Tuesday, March 28, 2006, 15:45–16:00, HSZ 301

High Field Magnetization and ESR on a S = 1 Spin Ladder — •C. Mennerich¹, C. Golze^1,2, V. Kataev², A. Alfonsov², R. Klingeler^2,3, B. Büchner², D.J. Price⁴, M. Goiran³, H. Rakoto³, J.-M. Broto³, O. Kataeva⁵, M. Broekelmann¹, S. Grossjohann⁶, W. Brenig⁶, and H.-H. Klauss¹ — ¹IPKM,TU Braunschweig, Germany — ²IfW Dresden, Germany — ³LNCMP Toulouse, France — ⁴U Glasgow, United Kingdom — ⁵Arbuzov Institute, RAS, Kazan, Russia — ⁶IThP, TU Braunschweig, Germany

The compound Na₂Ni₂(ox)₂(H₂O)₂ (ox =C₂O₄) forms a S=1 spin ladder. SQUID measurements show a pronouced maxima at temperatures between 39 K and 47 K along different crystallographic axes. This behaviour results from antiferromagnetic interactions and a single ion anisotropy D in the distorted octahedral surrounding of the Ni(II) ions. To determine the anisotropy D and the g-factor we performed high frequency (up to 740 GHz) high field (up to 30 T) ESR measurements on a powder sample resulting in D = 11.5 K and g = 2.2. Using these results we analysed the susceptibility and magnetization measurements. High field magnetization measurements up to 55 Tesla on a powder sample show typical magnetization steps in very good agreement with our simulations. These results prove that the system is close to the decoupled dimer limit. Further support for this conclusion stems from quantum monte carlo simulations performed for different ratios of intra-dimer to inter-dimer coupling taking into account the single ion anisotropy D.

This work is supported by the DFG within SPP1137 under contract KL1086/6-1.