Braided Ising spin-tube physics in a purported kagome magnet

TL;DR

This study reveals that Nd$_3$BWO$_9$'s magnetic properties are governed by inter-plane couplings, which can be modeled by a simple one-dimensional Ising spin-tube Hamiltonian, explaining its complex magnetic phenomena.

Contribution

The paper challenges previous kagome lattice interpretation and introduces a novel simple Ising spin-tube model to explain the magnetic behavior of Nd$_3$BWO$_9$.

Findings

Inter-plane couplings dominate the magnetic physics.

A simple Ising model captures ground state and excitations.

The model explains field-induced magnetization plateaus.

Abstract

The magnetic insulator Nd$_3$BWO$_9$ has been previously proposed to realize the highly frustrated breathing kagome lattice model. We report a combination of single-crystal neutron scattering studies and numerical simulations that debunk this interpretation. We show that it is the inter-plane couplings that determine the physics. To explain the exotic magnetism, we derive a simple one-dimensional Ising model composed of twisted triangular spin-tubes, i.e., triple braids of Ising spin chains with almost-orthogonal anisotropy frames and competing ferro-antiferromagnetic interactions. This model can account for the ground state, excitations, the numerous field-induced fractional magnetization plateau phases and incommensurate magnetic correlations at elevated temperatures. Nd$_3$BWO$_9$ constitutes a rare example where rich magnetic phenomena can be understood and simulated quantitatively in terms of a simple classical Hamiltonian.