Neutron diffraction studies on the multiferroic conical magnet BaMgFeO

Ishiwata, Shintaro*; Okuyama, Daisuke*; Kakurai, Kazuhisa; Nishi, Masakazu*; Taguchi, Yasujiro*; Tokura, Yoshinori*

Magnetic structure of a multiferroic Y-type hexaferrite BaMgFeO with helical-spin structures propagating along [001] below 195K has been extensively studied, using polarized and unpolarized neutron diffractions under transverse magnetic fields up to 4.5T. The magnetic phase diagram was investigated as a function of transverse B and coexistence of several phases with different helical-spin periodicity was confirmed at low-B region. By using the polarized neutron diffraction under transverse B, we verified that the ferroelectric phase with the largest electric polarization P with a commensurate k0 vector (0,0,3/2) has a transverse-conical structure. The relation between the transverse-conical spin structure and P as a function of the transverse B is discussed in terms of the inverse Dzyaloshinskii-Moriya model.