A new layered kagome strip structure Na2Co3(AsO4)2(OH)2: static and dynamic magnetic properties

Abstract

One-dimensional kagome strip chains share much of the same frustrated structural motif as two-dimensional kagome antiferromagnets, making them valuable for deepening our understanding of kagome lattice magnetism. In this paper, we report the hydrothermal synthesis and detailed structural and property characterization of Na₂Co₃(AsO₄)₂(OH)₂, a striped kagome system. The crystal structure was characterized using single crystal X-ray diffraction which reveals that Na₂Co₃(AsO₄)₂(OH)₂ crystallizes in monoclinic crystal system C2/m. The structure features a one-dimensional kagome strip lattice built from Co²⁺ ions and undergoes an antiferromagnetic transition at T_N = 14 K. The magnetic ground state at zero field was characterized using neutron powder diffraction. Below the magnetic transition, Na₂Co₃(AsO₄)₂(OH)₂ orders into an antiferromagnetic structure with a k-vector (0.5, 0.5, 0.5). In the proposed model, the Co1 moment is predominantly confined to the ac-plane while the Co2 moment is primarily aligned along the b-axis. Two flat bands were observed in the inelastic neutron spectra below the magnetic transition, 5 and 10 meV. Inelastic neutron spectra were modeled with a Heisenberg Hamiltonian including three nearest-neighbor exchange interactions (J₁, J₂, J₃) and strong single-ion anisotropy to stabilize the observed magnetic structure. Our study highlights the complexity of Co²⁺-based kagome strip magnetic lattice compound Na₂Co₃(AsO₄)₂(OH)₂ which provides an excellent platform to broaden our understanding of the frustrated kagome magnetic lattice space.