Macroscopic magnetic frustration

TL;DR

This paper demonstrates that macroscopic ferromagnetic rotors arranged in a planar lattice can exhibit spin ice behavior, providing a tangible, classical system to study geometrical frustration typically observed at microscopic scales.

Contribution

The authors introduce a macroscopic system of ferromagnetic rotors that exhibits spin ice rules, bridging microscopic phenomena with macroscopic, observable experiments.

Findings

System relaxes into honeycomb spin ice phase

Relaxation occurs on multiple time scales

Classical mechanical model explains the relaxation process

Abstract

Although geometrical frustration transcends scale, it has primarily been evoked in the micro and mesoscopic realm to characterize such phases as spin-ice liquids and glasses and to explain the behavior of such materials as multiferroics, high temperature superconductors, colloids and copolymers. Here we introduce a system of macroscopic ferromagnetic rotors arranged in a planar lattice capable of out-of-plane movement that exhibit the characteristic honeycomb spin ice rules studied and seen so far only in its mesoscopic manifestation. We find that a polarized initial state of this system settles into the honeycomb spin ice phase with relaxation on multiple time scales. We explain this relaxation process using a minimal classical mechanical model which includes Coulombic interactions between magnetic charges located at the ends of the magnets and viscous dissipation at the hinges. Our study shows how macroscopic frustration arises in a purely classical setting that is amenable to experiment, easy manipulation, theory and computation, and shows phenomena that are not visible in their microscopic counterparts.