Heliconical magnetic order and field-induced multiferroicity of the Co2Y-type hexaferrite Ba0.3Sr1.7Co2Fe12O22

Using magnetoelectric measurements and neutron diffraction, we investigated multiferroic properties of Co2Y hexaferrite Ba0.3Sr1.7Co2Fe12O22 in zero and finite magnetic field (H perpendicular to c). Upon zero-field cooling, a longitudinal heliconical magnetic structure was observed below 280 K, which involves incommensurate planar helical ordering. When the magnetic field was applied perpendicular to its c axis, electric polarization was observed and the incommensurate ordering was replaced by a commensurate one as commonly observed in other hexaferrites. Electric polarization remained at its maximum during field reversal at 10 K, which indicates that magnetic anisotropy within the basal planes stabilizes the field-induced electric polarization.