Magnetic density of states at low energy in geometrically frustrated systems

TL;DR

This study reveals persistent low-temperature spin dynamics in the pyrochlore Gd2Ti2O7, linked to a low-energy magnetic density of states with an upturn and a temperature-dependent gap, suggesting a common feature in frustrated magnets.

Contribution

It demonstrates persistent spin dynamics in Gd2Ti2O7 below 1 K and proposes a generic low-energy density of states in geometrically frustrated systems.

Findings

Persistent spin dynamics observed down to 20 mK.

Muon relaxation explained by magnetic excitation scattering.

Low-energy density of states with an upturn and linear temperature-dependent gap.

Abstract

Using muon-spin-relaxation measurements we show that the pyrochlore compound Gd2Ti2O7, in its magnetically orderered phase below ~ 1 K, displays persistent spin dynamics down to temperatures as low as 20 mK. The characteristics of the induced muon relaxation can be accounted for by a scattering process involving two magnetic excitations, with a density of states characterized by an upturn at low energy and a small gap depending linearly on the temperature. We propose that such a density of states is a generic feature of geometrically frustrated magnetic materials.