Hidden energy scale and the effects of quenched disorder in geometrically frustrated magnets

Quenched disorder in geometrically frustrated magnets (GFMs) may prevent the formation of the widely sought quantum-spin-liquid states and lead to the formation of spin-glass states, incompatible with a quantum spin liquid. Our analyses of the available experimental data on the spin-glass-freezing transition in GFMs as a function of the amount of quenched disorder demonstrate the existence of a ``hidden energy scale’’ that determines the order of magnitude of the temperature of the spin-glass freezing in a broad class of GFMs and is a property of a clean material.

In this work, we propose a scenario of the hidden energy scale and demonstrate further evidence for the hidden energy scale in the thermodynamic properties of GFMs and neutron scattering intensity. We demonstrate that the hidden energy scale comes from low-energy excitations adiabatically connected to the Ising states on the magnetic lattice of the material. We also develop a microscopic theory of spin-glass freezing in GFMs and show that increasing the density of vacancy defects, the most common form of quenched disorder in GFMs, lowers the glass-transition temperature at small defect densities.