Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: Correlated Electrons: Low-dimensional Systems - Materials 3
TT 40.11: Talk
Thursday, March 29, 2012, 17:45–18:00, H 0104
Field driven ordering in a frustrated spin ladder with bond randomness — •Erik Wulf1, Sebastian Mühlbauer1, Tatiana Yankova1,2, and Andrey Zheludev1 — 1Neutron Scattering and Magnetism Group, Laboratory for Solid State Physics, ETH Zürich, Zürich, Switzerland — 2Chemistry Department, M. V. Lomonosov Moscow State University, Moscow, Russia
We studied the influence of bond randomness on field driven magnon ordering in a frustrated 4-leg ladder. Weak interladder interactions and strong coupling along the ladder legs characterize the almost perfect 1D behavior of H8 C4 SO2 · Cu2 Cl4. By overcoming the critical field of Hc =3.7T the gap between singlet ground state and excited triplet state is closed. The material undergoes a phase transition from spin liquid to long-range spiral order. Chemical substitution of the nonmagnetic Cl- ions by Br- ions causes bond disorder in H8 C4 SO2 · Cu2 ( Cl1-x Brx )4. The effect on the phase transition was characterized by measurements of the magnetization and the specific heat [1]. It was shown that already low Br- concentrations of x=1% replace the phase transition by a crossover. While the specific heat data of the pure material exhibit a sharp λ-anomaly the data measured at x ≥ 1% show a broad peak. The same behavior is observed in the susceptibility data. In contrast to the transition the critical field itself is almost unaffected.
This work is partially supported by the Swiss National Science Foundation under project 6 of the Materials with Novel Electronic Properties program.
E. Wulf, S. Mühlbauer, T. Yankova and A. Zheludev, Phys. Rev. B 85, 174414 (2011).