μSR Measurements of the Magnetism of Sr₃Fe₂O₇

We present a preliminary report of zero and transverse field μSR measurements in a high quality single crystal of fully oxygenated Sr₃Fe₂O₇[1], the insulating 3d magnetic analogue of the well studied Sr₃Ru₂O₇, in its charge-disproportionated state, through the magnetic transition to the incommensurate phase at T_N ~ 115 K. A very broad distribution of static fields below T_n yields a large (2/3) missing fraction. Rapidly damped zero field oscillations indicate a large internal field at the muon, estimated to be 0.46 T at 0 K. In the paramagnetic state, we find two muon precession frequencies at 0.25 T applied field, reminiscent of the Mössbauer spectra.