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arXiv · 1807.09605

Anharmonic magnon excitations in noncollinear and charge-ordered RbFe$^{2+}$Fe$^{3+}$F$_6$

M. Songvilay·E. E. Rodriguez·R. Lindsay·M. A. Green·H. C. Walker·J. A. Rodriguez-Rivera·C. Stock
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Abstract

RbFe$^{2+}$Fe$^{3+}$F$_6$ is an example of a charge ordered antiferromagnet where iron sites, with differing valences, are structurally separated into two interpenetrating sublattices. The low temperature magnetically ordered Fe$^{2+}$ ($S$=2) and Fe$^{3+}$ ($S$=5/2) moments form a noncollinear orthogonal structure with the Fe$^{3+}$ site displaying a reduced static ordered moment. Neutron spectroscopy on single crystals finds two distinct spin wave branches with a dominant coupling along the Fe$^{3+}$ chain axis ($b$-axis). High resolution spectroscopic measurements find an intense energy and momentum broadened magnetic band of scattering bracketing a momentum-energy region where two magnon processes are kinematically allowed. These anharmonic excitations are enhanced in this non collinear magnet owing to the orthogonal spin arrangement.

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M. Songvilay, E. E. Rodriguez, R. Lindsay, M. A. Green, H. C. Walker, J. A. Rodriguez-Rivera, C. Stock. 2018-07-25. Anharmonic magnon excitations in noncollinear and charge-ordered RbFe$^{2+}$Fe$^{3+}$F$_6$. https://doi.org/10.1103/physrevlett.121.087201

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