Thermal evolution of quasi-1D spin correlations within the anisotropic triangular lattice of $\alpha$-NaMnO${}_2$

Abstract

Magnetic order on the spatially anisotropic triangular lattice of $\alpha$-NaMnO${}_2$ is studied via neutron diffraction measurements. The transition into a commensurate, collinear antiferromagnetic ground state with $\mathbf{k}=(0.5,0.5,0)$ was found to occur below $T_{\mathrm{N}}=22$ K. Above this temperature, the transition is preceded by the formation of a coexisting, short-range ordered, incommensurate state below $T_{\mathrm{IC}}=45$ K whose two dimensional propagation vector evolves toward $\mathbf{k}=(0.5,0.5)$ as the temperature approaches $T_{\mathrm{N}}$. At high temperatures ($T>T_{\mathrm{IC}}$), quasielastic scattering reveals one-dimensional spin correlations along the nearest neighbor Mn-Mn "chain direction" of the MnO${}_6$ planes. Our data are consistent with the predictions of a mean field model of Ising-like spins on an anisotropic triangular lattice, as well as the predominantly one-dimensional Heisenberg spin Hamiltonian reported for this material.

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Cited by in corpus (6)

• High order magnon bound states in the quasi-one-dimensional antiferromagnet $\alpha$-NaMnO${}_2$
• Dark Field X-ray Microscopy Below Liquid-Helium Temperature: The Case of NaMnO2
• Nanoscale degeneracy lifting in a geometrically frustrated antiferromagnet
• Structural modulation in potassium birnessite single crystals
• Cluster glass behavior of frustrated birnessites AxMnO2*yH2O (A = Na, K)
• Metastable and localized Ising magnetism in $\alpha$-CoV${}_2$O${}_6$ magnetization plateaus