Direct evidence for a dynamical ground state in the highly frustrated Tb$_2$Sn$_2$O$_7$ pyrochlore

TL;DR

This study provides direct evidence of persistent spin dynamics in Tb$_2$Sn$_2$O$_7$, indicating a dynamical ground state with strong fluctuations and correlated spin cluster behavior below the ferromagnetic transition.

Contribution

It demonstrates that Tb$_2$Sn$_2$O$_7$ exhibits a dynamical ground state with persistent fluctuations, challenging the notion of static order in this highly frustrated pyrochlore.

Findings

Muon relaxation remains dynamical below T_C

Hints of long-range order appear under external field

Hysteresis observed below T_C

Abstract

MuSR experiments have been performed on powder sample of the "ordered spin ice" Tb$_2$Sn$_2$O$_7$ pyrochlore compound. At base temperature (T=35mK) the muon relaxation is found to be of dynamical nature which demonstrates that strong fluctuations persist below the ferromagnetic transition (T_C=0.87K). Hints of long range order appear as oscillations of the muon polarization when an external field is applied and also as a hysteretic behavior below T_C. We propose a dynamical and strongly correlated scenario where dynamics results from fluctuation of large spin clusters with the "ordered spin ice" structure.