Macroscopic signature of protected spins in a dense frustrated magnet

TL;DR

This paper demonstrates how optical hole-burning techniques can probe protected spin clusters in a frustrated magnet, clarifying previous experimental discrepancies and revealing the macroscopic signatures of these protected states.

Contribution

It introduces a magnetic analogue of optical hole-burning to study protected spins in a frustrated magnet, providing new insights into their macroscopic behavior.

Findings

Identification of protected spin clusters in gadolinium gallium garnet

Resolution of discrepancies between magnetometry and neutron diffraction

Evidence of macroscopic signatures of protected states

Abstract

The inability of systems of interacting objects to satisfy all constraints simultaneously leads to frustration. A particularly important consequence of frustration is the ability to access certain protected parts of a system without disturbing the others. For magnets such "protectorates" have been inferred from theory and from neutron scattering, but their practical consequences have been unclear. We show that a magnetic analogue of optical hole-burning can address these protected spin clusters in a well-known, geometrically frustrated Heisenberg system, gadolinium gallium garnet. Our measurements additionally provide a resolution of a famous discrepancy between the bulk magnetometry and neutron diffraction results for this magnetic compound.