Neutron Scattering Study of a Frustrated Kagome-Strip Structure: Na2Co3(AsO4)2(OH)2

TL;DR

This study explores the magnetic properties of a new material with a unique Kagome-strip structure, revealing antiferromagnetic behavior and high magnetic frustration.

Contribution

The paper reports the synthesis and magnetic characterization of a new Kagome-strip compound with S = 3/2 Co2+ ions and identifies its antiferromagnetic ordering and metamagnetic transition.

Findings

Antiferromagnetic ordering occurs at 14 K and transitions to ferromagnetic behavior above 40 kOe.

Magnetic moments of Co(1) and Co(2) lie in the bc-plane with distinct orientations.

The compound exhibits high magnetic frustration, offering a model for studying transition metal arsenates and vanadates.

Abstract

The Na2Co3(AsO4)2(OH)2 structure has garnered interest owing to its mix of two-dimensional honeycomb and Kagome lattice features to form a Kagome-strip motif of S = 3/2 high-spin Co2+ metal centers. The Kagome-strip is believed to possess the same magnetically frustrated interactions as its parent honeycomb and Kagome lattices, both of which are well-known for their high magnetic frustration potential. Single crystals of Na2Co3(AsO4)2(OH)2 were prepared via a hydrothermal method. The pink columnar crystals crystallize in C2/m with cell parameters of a = 14.5885(9), b = 5.9376(3), and c = 5.0992(3) Å with β = 103.63(2)°. Magnetization studies show antiferromagnetic ordering at 14 K that is suppressed through a metamagnetic antiferro- to ferromagnetic transition that occurs at applied fields greater than 40 kOe, as revealed by isothermal field-dependent magnetization studies below 14 K. Magnetic structure determination by powder neutron diffraction yielded a k-vector of (0.5,0.5,0.5), confirming the antiferromagnetic behavior in low-field magnetization.

Both Co(1) and Co(2) moments lie in the bc-plane. Specifically, the Co(1) moments point along the c-axis, while the Co(2) moments rest along the b-axis. Magnetic studies presented herein suggest a highly frustrated system with complimentary powder neutron diffraction data providing a pathway for additional transition metal arsenate and vanadate analogs each with their own unique magnetic interactions owing to a difference in the transition metals themselves and in the interaction pathways afforded through p- and d-orbitals in the respective arsenate and vanadates.