Domain rearrangement and spin-spiral-plane flop as sources of magnetoelectric effects in delafossite CuCrO2

Using neutron scattering, we elucidate the origins of magnetoelectric effects observed in a triangular lattice antiferromagnet, CuCrO2, showing a ferroelectricity associated with a spiral-spin order (T-N1 similar to 24 K). Below T-*similar to 16 K, we observed a remarkable difference in the magnetic Bragg reflection and the electric polarization P between their zero-field-cooling (ZFC) and field-cooling procedures, suggesting that the distribution of magnetic domains coupled with electric ones depends on their cooling procedure. We further demonstrate that one of the domains surviving after the ZFC procedure exhibits a sudden flop of the spiral-spin plane by applying a magnetic field, which is ascribed to the flop of P observed in CuCrO2.