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arXiv · 1901.09617

Flat-band spin dynamics and phonon anomalies of the saw-tooth spin-chain system Fe$_2$O(SeO$_3$)$_2$

V. P. Gnezdilov·Yu. G. Pashkevich·V. S. Kurnosov·O. V. Zhuravlev·D. Wulferding·P. Lemmens·D. Menzel·E. S. Kozlyakova·A. Yu. Akhrorov·E. S. Kuznetsova·P. S. Berdonosov·V. A. Dolgikh·O. S. Volkova·A. N. Vasiliev
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Abstract

Fe$^{3+}$ $S = 5/2$ ions form saw-tooth like chains along the $a$ axis of the oxo-selenite Fe$_2$O(SeO$_3$)$_2$ and an onset of long-range magnetic order is observed for temperatures below $T_C = 105$ K. This order leads to distinct fingerprints in phonon mode linewidths and energies as resolved by Raman scattering. In addition, new excitations with small linewidths emerge below $T = 150$ K, and are assigned to two-magnon scattering processes with the participation of flat-band and high energy magnon branches. From this a set of exchange coupling constants is estimated. The specific ratio of the saw-tooth spine-spine and spine-vertex interactions may explain the instability of the dimer quantum ground state against an incommensurate 3D magnetic order.

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V. P. Gnezdilov, Yu. G. Pashkevich, V. S. Kurnosov, O. V. Zhuravlev, D. Wulferding, P. Lemmens, D. Menzel, E. S. Kozlyakova, A. Yu. Akhrorov, E. S. Kuznetsova, P. S. Berdonosov, V. A. Dolgikh, O. S. Volkova, A. N. Vasiliev. 2019-01-28. Flat-band spin dynamics and phonon anomalies of the saw-tooth spin-chain system Fe$_2$O(SeO$_3$)$_2$. https://doi.org/10.1103/physrevb.99.064413

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