A classification of spin frustration in molecular magnets from a physical study of large odd-numbered-metal, odd electron rings

TLDR

Frustration, originally coined by Anderson to describe competing antiferromagnetic interactions, has become central to condensed‑matter studies of spin glasses, kagomé lattices, and emergent phenomena such as magnetic monopoles in spin ice. The study aims to synthesize and characterize nine‑metal rings to investigate their frustrated magnetic behavior. The authors synthesized the rings and probed their magnetic properties with magnetometry and inelastic neutron scattering, complemented by density‑functional theory calculations. The compounds exhibit distinct electronic and magnetic structures driven by frustration, prompting the authors to propose a comprehensive classification of frustration in molecular magnets.

Abstract

The term “frustration” in the context of magnetism was originally used by P. W. Anderson and quickly adopted for application to the description of spin glasses and later to very special lattice types, such as the kagomé. The original use of the term was to describe systems with competing antiferromagnetic interactions and is important in current condensed matter physics in areas such as the description of emergent magnetic monopoles in spin ice. Within molecular magnetism, at least two very different definitions of frustration are used. Here we report the synthesis and characterization of unusual nine-metal rings, using magnetic measurements and inelastic neutron scattering, supported by density functional theory calculations. These compounds show different electronic/magnetic structures caused by frustration, and the findings lead us to propose a classification for frustration within molecular magnets that encompasses and clarifies all previous definitions.