A New Layered Kagome Strip Structure Na2Co3(AsO4)2(OH)2: Static and Dynamic Magnetic Properties

TL;DR

This study synthesizes and characterizes a new one-dimensional kagome strip compound Na2Co3(AsO4)2(OH)2, revealing its magnetic structure, transition at 14 K, and complex magnetic excitations, advancing understanding of frustrated kagome magnetism.

Contribution

It reports the first detailed structural and magnetic analysis of Na2Co3(AsO4)2(OH)2, a novel kagome strip system, including neutron diffraction and inelastic spectra modeling.

Findings

Antiferromagnetic transition at 14 K

Complex magnetic structure with distinct Co moments

Observation of flat bands at 5 and 10 meV

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 the monoclinic crystal system C2/m. The structure features a one-dimensional kagome strip lattice built from Co2+ ions and undergoes an antiferromagnetic transition at TN = 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 at 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 the 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.