Neutron scattering study of magnetic structure in triangle spin tube CsCrF$_4$

Triangle spin tube viewed from tube direction is topologically equivalent to kagomé lattice. The rung ($J_1$) and inter-tube ($J_2$) interactions on triangle spin tube correspond respectively to the next nearest neighbor and the nearest neighbor interactions on kagomé lattice. In the case of $J_1 > 0$ (Antiferromagnetic) and $ J_1 >> |J_2|$, the ground state is $q = 0, 120^\circ$ structure with $J_2 > 0$ or Cuboc state that represented multi-$q$ ($q = 2\pi(1/2~0)$ and two symmetric-equivalent vectors) with $J_2 < 0$ [1]. CsCrF$_4$ is a perfect triangle spin tube material with antiferromagnetic intra-tube and rung interactions [2]. Neutron diffraction measurement revealed magnetic long-range order at $T = 1.5~\rm{K}$. Contrary to the expectation, the magnetic structure was determined $q = 2\pi(1/2~0~1/2)$, $120^\circ$ structure by Rietveld refinement. We also confirmed that this structure was stabilized by Dzyaloshinskii -Moriya interaction and small anisotropy that obeyed the three-fold symmetry at Cr sites by calculation. [1] H. Ishikawa et al., JPSJ 83, 043703 (2014). [2] H. Manaka et al., JPSJ 78, 093701 (2009).