Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 13: Correlated Electrons: Low-dimensional Systems - Materials 1

TT 13.10: Vortrag

Dienstag, 26. Februar 2008, 12:00–12:15, H 2053

Magnetic properties of the Haldane-gap material NENB — •Erik Čižmár¹, Mikhaylo Ozerov¹, Oleg Ignatchik¹, Thomas P. Papageorgiou¹, J. Wosnitza¹, S. A. Zvyagin¹, Jurek Krzystek², Zhixian Zhou³, Christopher P. Landee⁴, Brian R. Landry⁴, Mark M. Turnbull⁴, and Jan L. Wikaira⁵ — ¹Hochfeld-Magnetlabor Dresden (HLD), Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany — ²National High Magnetic Field Laboratory, Tallahassee, USA — ³Department of Physics and Astronomy, Wayne State University, Detroit, USA — ⁴Department of Physics and Carlson School of Chemistry, Clark University, Worcester, USA — ⁵Department of Chemistry, University of Canterbury, Christchurch, New Zealand

Results of magnetization and high-field ESR studies of the new spin-1 Haldane-chain material [Ni(C₂H₈N₂)₂NO₂](BF₄) (NENB) are reported. A definite signature of the Haldane state in NENB was obtained. From the analysis of the frequency-field dependence of magnetic excitations in NENB, the spin-Hamiltonian parameters were calculated, yielding Δ/k_B = 17.4 K, g_∥=2.14, D/k_B=7.5 K, and |E/k_B|=0.7 K for the Haldane gap, g factor. and the crystal-field anisotropy, respectively. The presence of fractional S=1/2 chain-end states, revealed by ESR and magnetization measurements, is found to be responsible for spin-glass-freezing effects. In addition, extra states in the excitation spectrum of NENB have been observed in the vicinity of the Haldane gap, whose origin is discussed.
The work was supported in part by the DFG through Grant No. ZV 6/1-1.