Ising spin ladders of orthopyroxene CoGeO$_3$

TL;DR

This study investigates the magnetic properties of CoGeO$_3$, demonstrating it as an Ising spin ladder with non-collinear order stabilized by local anisotropy, supported by thermodynamic, spectroscopic, and neutron scattering data.

Contribution

It provides the first detailed magnetic Hamiltonian for CoGeO$_3$, establishing it as a realization of an Ising spin ladder with anisotropy-driven magnetic order.

Findings

Non-collinear magnetic order below 32 K stabilized by local easy-axis anisotropy.

Extraction of a magnetic Hamiltonian supports the Ising spin ladder model.

Inelastic neutron scattering confirms the effective magnetic interactions.

Abstract

We present thermodynamic and spectroscopic measurements for an orthopyroxene CoGeO$_3$ with magnetic Co$^{2+}$ ions that form quasi-one-dimensional ladders. We show that non-collinear magnetic order below $T_N$=32 K can be stabilized by a strong local easy-axis anisotropy of $j_\text{eff}=1/2$ moments, which is induced by ligand octahedra distortions. Extraction of a magnetic Hamiltonian from inelastic neutron scattering measurements supports this interpretation and allows us to establish an effective magnetic model. The resulting exchange Hamiltonian justifies CoGeO$_3$ as a realization of an Ising spin ladder compound.