Title: Spin dynamics in the pyrochlore iridate, Er2Ir2O7, investigated by muSR spectroscopy

Abstract: Building a full understanding of the complex magnetism in the rare-earth pyrochlore iridates, A2Ir2O7, is an ongoing issue in condensed matter physics. The possibility of two interpenetrating and interacting frustrated magnetic pyrochlore sublattices, connected with the strong spin-orbit coupling of the 5d Ir4+ ion, lends itself to a wide array of potential electronic and magnetic states. In this paper, we present longitudinal field and zero field muSR measurements of Er2Ir2O7. The muSR response of Er2Ir2O7 is dominated by the strong fluctuating fields of the Er3+ (J = 15/2) moments, showing a peak in fitted relaxation rate, {\lambda}_2, at T = 15 K . The muSR spectra show just weak signatures of the Ir transition, that were easily suppressed in applied longitudinal field, however full decoupling of the muons from local magnetic fields was not achieved even in applied fields up to 3 kG.