Two-dimensional short-range spin-spin correlations in the layered spin- 32 maple leaf lattice antiferromagnet Na2Mn3O7 with crystal stacking disorder

Abstract

We report the nature of magnetic structure, and microscopic spin-spin correlations and their dependence on the underlying crystal structure of the geometrically frustrated layered spin-$\frac{3}{2}$ maple leaf lattice (MLL) antiferromagnet ${\mathrm{Na}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{7}$ by a comprehensive neutron diffraction study. Crystal structural studies by x-ray and neutron diffraction reveal that the MLL layers (constituted by ${\mathrm{Mn}}_{3}{\mathrm{O}}_{7}{}^{2\ensuremath{-}}$ units) are well separated by nonmagnetic Na layers. The studies also conclude the presence of stacking faults (in-plane sliding of magnetic MLL layers) as well as a distortion in the MLL of ${\mathrm{Mn}}^{4+}$. Temperature dependent magnetic susceptibility, heat capacity, and neutron diffraction data yield a short-range antiferromagnetic (AFM) ordering below $\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ without a long-range magnetic ordering down to 1.5 K. The analysis of the diffuse magnetic neutron scattering patterns by the reverse Monte Carlo method reveals two-dimensional (2D) spin-spin correlations within the MLL layers. Additionally, we establish a relation between the correlation length of the short-range magnetic ordering with the stacking faults through a varying synthesis condition. The present study, therefore, explores a microscopic picture of the crystal and spin structures, as well as their correlation; hence it provides experimental insight of the magnetic ordering in a MLL AFM. Further, we have outlined the formation of several 2D frustrated lattice geometries having triangular plaquettes, including the MLL, by crystal engineering of the triangular lattice, and their role in the stabilization of multiple unique chiral spin states which opens up the door for study of unique chiral spin states.