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arXiv · 1005.1474

Anisotropy of Magnetic Interactions in the Spin-Ladder Compound (C$_5$H$_{12}$N)$_2$CuBr$_4$

E. Čižmár·M. Ozerov·J. Wosnitza·B. Thielemann·K. W. Krämer·Ch. Rüegg·O. Piovesana·M. Klanjšek·M. Horvatić·C. Berthier·S. A. Zvyagin
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Abstract

Magnetic excitations in the spin-ladder material (C$_5$H$_{12}$N)$_2$CuBr$_4$ [BPCB] are probed by high-resolution multi-frequency electron spin resonance (ESR) spectroscopy. Our experiments provide a direct evidence for a biaxial anisotropy ($\sim 5\%$ of the dominant exchange interaction), that is in contrast to a fully isotropic spin-ladder model employed for this system previously. It is argued that this anisotropy in BPCB is caused by spin-orbit coupling, which appears to be important for describing magnetic properties of this compound. The zero-field zone-center gap in the excitation spectrum of BPCB, $\Delta_0/k_{B}=16.5$ K, is detected directly. Furthermore, an ESR signature of the inter-ladder exchange interactions is obtained. The detailed characterization of the anisotropy in BPCB completes the determination of the full spin hamiltonian of this exceptional spin-ladder material and shows ways to study anisotropy effects in spin ladders.

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E. Čižmár, M. Ozerov, J. Wosnitza, B. Thielemann, K. W. Krämer, Ch. Rüegg, O. Piovesana, M. Klanjšek, M. Horvatić, C. Berthier, S. A. Zvyagin. 2010-05-10. Anisotropy of Magnetic Interactions in the Spin-Ladder Compound (C$_5$H$_{12}$N)$_2$CuBr$_4$. https://doi.org/10.1103/physrevb.82.054431

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