Magnetic-Field Controllable Displacement-Type Ferroelectricity Driven by Off-Center Fe²⁺ Ions in CaFe₃Ti₄O₁₂ Perovskite

Displacement-type ferroelectrics usually exclude magnetic d-electron contribution. Applying a magnetic field thus can little change the electric polarization. Herein, a magnetic ionic driven displacement-type perovskite ferroelectric CaFe₃Ti₄O₁₂ is reported. In this compound, magnetic Fe²⁺ ions contribute to both ferroelectric and antiferromagnetic orders respectively at T_C ≈107 and T_N ≈ 3.1 K, resulting in coupled electric and magnetic domains. A moderate magnetic field can induce a metamagnetic transition toward ferromagnetic correlations. External magnetic fields can thus readily tune the magnetic and the joint ferroelectric domains, giving rise to exceptional magnetic-field controllable displacement-type polarization with a large magnetoelectric (ME) coupling coefficient. This study opens up a new avenue to find unprecedented ME effects in displacement-type ferroelectrics for numerous applications.