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arXiv · 2006.06273

Spin-chain correlations in the frustrated triangular lattice material CuMnO$_2$

Simon A. J. Kimber·Andrew Wildes·Hannu Mutka·Jan-Willem G. Bos·Dimitri N. Argyriou
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Abstract

The Ising triangular lattice remains the classic test-case for frustrated magnetism. Here we report neutron scattering measurements of short range magnetic order in CuMnO$_2$, which consists of a distorted lattice of Mn$^{3+}$ spins with single-ion anisotropy. Physical property measurements on CuMnO$_2$ are consistent with 1D correlations caused by anisotropic orbital occupation. However the diffuse magnetic neutron scattering seen in powder measurements has previously been fitted by 2D Warren-type correlations. Using neutron spectroscopy, we show that paramagnetic fluctuations persist up to $\sim$25 meV above TN= 65 K. This is comparable to the incident energy of typical diffractometers, and results in a smearing of the energy integrated signal, which hence cannot be analysed in the quasi-static approximation. We use low energy XYZ polarised neutron scattering to extract the purely magnetic (quasi)-static signal. This is fitted by reverse Monte Carlo analysis, which reveals that two directions in the triangular layers are perfectly frustrated in the classical spin-liquid phase at 75 K. Strong antiferromagnetic correlations are only found along the b-axis, and our results hence unify the pictures seen by neutron scattering and macroscopic physical property measurements.

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Simon A. J. Kimber, Andrew Wildes, Hannu Mutka, Jan-Willem G. Bos, Dimitri N. Argyriou. 2020-06-11. Spin-chain correlations in the frustrated triangular lattice material CuMnO$_2$. https://doi.org/10.1088/1361-648x/ab9d4b

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