Multiferroicity in Calcium Manganate via Strain Engineering

Multiferroics have attracted intense interest due to their potential applications in multifunctional devices and high‐density storage for the next‐generation electronic technologies, owing to their multiple ferroic orders, especially ferroelectric and magnetic ones. However, the symmetry constraints imposed by magnetic point groups and the electronic configuration conflicts in d orbitals between ferroelectricity and magnetism hinder the coexistence of ferroelectric and magnetic orders, leading to a scarcity of multiferroics. In this work, multiferroicity is achieved in the non‐ferroelectric magnet Calcium Manganate (CaMnO3) through tensile‐strain engineering. The ferroelectricity with a Curie temperature up to 45 K is evidenced by the polarization‐electric field (P‐E) hysteresis loops, which also suggest that the spontaneous polarization aligns along [100] and [010] directions. Meanwhile, the magnetization below 125 K is confirmed by both the magnetization hysteresis loops and the temperature‐dependent magnetization measurements, providing compelling evidence for the multiferroic nature in the tensile‐strained CaMnO3 films. In addition, an abrupt increase in magnetization is found below 10K, indicating the establishment of a new ferromagnetic order due to the suppression of thermal fluctuations. These findings highlight strain engineering as a universal strategy to induce multiferroicity in non‐ferroelectric magnets.