IMF2017

BiFeO₃ is the most promising single-phase multiferroic material due to its large polarization and high operating temperature and draws many attentions. As a typical type-I multiferroic material, the magnetoelectric coupling in BiFeO₃ is deemed to be weak due to the different origins of its ferroelectricity and magnetism. Here, the magnetoelectric effect in bulk BiFeO₃ is readdressed both theoretically and experimentally. Based on the DM interaction scenario, the magnetoelectric effect in BiFeO₃ is actually strong, with a coupling energy of about 1.25 meV and a magnetism-coupled parasitic polarization comparable to that of the type-II multiferroics. However, such strong magnetoelectric coupling also causes the cycloidal spin structure, which inhibits the observation of linear magnetoelectric coupling in bulk BiFeO₃. To resolve this contradiction, Sm-substitution is utilized to suppress the magnetoelectric effect and unlocks the weak ferromagnetism. At an optimized composition, such weak ferromagnetic state can be switched back to the cycloidal state by electric field, thus realizing electrically controlling of the magnetism. It has been argued that field-controlled phase transition is a promising path to colossal magnetoelectric effect.