Spin dynamics in the double-pyrochlore compound Er2Ru2O7

Er2Ru2O7 possesses a cubic pyrochlore structure with Ru4+ and Er3+ orderings reported at 90 K and 10 K respectively. However, below 20 K neutron diffraction shows the polarization of Er3+ induced by the internal field of Ru4+ until the Er3+ following q = 0 magnetic structure at 3 K, while the magnetic moment significantly increases below 10 K; but even at 5 K, Er3+ still remains dynamic [1]. Intriguingly, neutron diffraction spectrum of Er2Ru2O7 reveals an exotic magnetic structure which does not follow conventional q = 0 magnetic order of pyrochlore lattice symmetry at 270 mK [2]. We propose to use muon spectroscopy to study the spin dynamics in a polycrystalline sample Er2Ru2O7 for all temperature ranges from 100 K down to 1.8 K on MuSR. This work will allow us to investigate the orderings and dynamics of both the Ru and Er moments, as well as the interplay between the two magnetic sublattices which may lead to the realization of a magnetic symmetry broken in a canonical XY magnet of Er2Ti2O7 [3]. Er2Ti2O7 had been studied successfully at ISIS using pulsed muon source [4]. To our knowledge, Er2Ru2O7 had been studied rarely, and had never been studied by muons before.