Two-dimensional short-range spin-spin correlations in the layered spin-3/2 maple leaf lattice antiferromagnet Na2Mn3O7 with crystal stacking disorder

Abstract

We report the nature of magnetic structure, microscopic spin-spin correlations and their dependence on the underlying crystal structure of the geometrically frustrated layered spin-3/2 maple-leaf-lattice (MLL) antiferromagnet Na2Mn3O7 by a comprehensive neutron diffraction study. Crystal structural studies by x-ray and neutron diffractions reveal that the MLL layers (constituted by Mn3O72- units) are well separated by non-magnetic 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 Mn4+. Temperature dependent magnetic susceptibility, heat capacity, and neutron diffraction data yield a short-range antiferromagnetic (AFM) ordering below ~ 100 K without a long-range magnetic ordering down to 1.5 K. The analysis of the diffuse magnetic neutron scattering patterns by reverse Monte Carlo method reveals 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, provides an experimental insight of the magnetic ordering in a MLL AFM. Further, we have outlined the formation of several 2D frustrated lattice geometry having triangular plaquettes, including the MLL, by crystal engineering of the triangular lattice and their role on the stabilization of multiple novel chiral spin states which opens up a door for study of novel chiral spin states.

26 pages, 10 figures, 1 table

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