Distorted Kagome Lattice Generated by a Unique Orbital Arrangement in the Copper Mineral KCu3As2O7(OH)3

TL;DR

This study investigates a new kagome antiferromagnet, KCu3As2O7(OH)3, revealing a highly distorted lattice with unique orbital arrangements that lead to complex magnetic interactions and long-range order at low temperatures.

Contribution

It identifies a novel orbital configuration in a kagome lattice that results in a highly distorted structure with unique magnetic properties.

Findings

Antiferromagnetic order at T_N = 7.2 K

Gradual spin entropy release below T_N

Presence of geometrical frustration in the distorted kagome lattice

Abstract

We study polycrystalline samples of KCu3As2O7(OH)3, a new candidate spin-1/2 kagome antiferromagnet, by magnetic susceptibility and heat capacity measurements above 2 K. The unique arrangement of the 3z2 - r2 and x2 - y2 orbitals on the Cu2+ kagome net is noted and compared to the orbital patterns found in other kagome minerals. It is suggested that this orbital arrangement gives rise to one antiferromagnetic and two ferromagnetic interactions on isosceles triangles forming a highly distorted kagome lattice. KCu3As2O7(OH)3 is found to show an antiferromagnetic long-range order at T_N = 7.2 K. Remarkably, a spin entropy is more gradually released upon cooling below T_N compared with a conventional magnetic long-range order, which may originate from the geometrical frustration still present in this highly distorted kagome lattice.