investigated with spin polarized positive muons*

The bulk properties of the prototypical linear magneto-electric antiferromagnet Cr₂O₃ have been extensively studied. Here, we report on a muon spin rotation (μSR) study using spin polarized muons to probe the local magneto-electric response in order to investigate magnetoelectricity on a microscopic level. We find that the muon, a light interstitial probe, occupies several distinct stopping sites in Cr₂O₃, and displays a rich dynamic behavior that we interpret in the context of local muon hopping and thermally activated site transitions. Furthermore, when Cr₂O₃ is prepared in a single magnetic domain, a shift in the local magnetic field is observed in response to an applied electric field, with the sign of the shift depending both on the field direction and domain state. The origin of this apparent magneto-electric effect is discussed.