Evidence of Magnon-Mediated Orbital Magnetism in a Quasi-2D Topological Magnon Insulator

TL;DR

This study investigates how topological and thermal effects influence orbital magnetism and spin dynamics in a quasi-2D topological magnon insulator, revealing temperature-dependent anisotropies linked to orbital moments and spin chirality.

Contribution

It demonstrates the temperature-dependent role of electronic and topological orbital moments in the anisotropic g-factor of a quasi-2D topological magnon insulator, highlighting the interplay of topology, spin chirality, and orbital magnetism.

Findings

g-factor anisotropy varies with temperature and is linked to orbital moments.

Electronic orbital moment influences g-anisotropy at low T.

Topological orbital moment dominates at higher T, affecting spin chirality.

Abstract

We explore spin dynamics in Cu(1,3-bdc), a quasi-2D topological magnon insulator. The results show that the thermal evolution of Land\'e $g$-factor ($g$) is anisotropic: $g_\textrm{in-plane}$ reduces while $g_\textrm{out-plane}$ increases with increasing temperature $T$. Moreover, the anisotropy of the $g$-factor ($\Delta g$) and the anisotropy of saturation magnetization ($\Delta M_\textrm{s}$) are correlated below 4 K, but they diverge above 4 K. We show that the electronic orbital moment contributes to the $g$ anisotropy at lower $T$, while the topological orbital moment induced by thermally excited spin chirality dictates the $g$ anisotropy at higher $T$. Our work suggests an interplay among topology, spin chirality, and orbital magnetism in Cu(1,3-bdc).