Hybrid Improper Ferroelectricity: A Mechanism for Controllable Magnetization-Polarization Coupling
Abstract
First-principles calculations are presented for the layered perovskite Ca3Mn2O7. The results reveal a rich set of coupled structural, magnetic and polar domains in which oxygen octahedron rotations induce ferroelectricity, magnetoelectricity and weak-ferromagnetism. The key point is that the rotation distortion is a combination of two non-polar modes with different symmetries. We use the term "hybrid" improper ferroelectricity to describe this phenomenon and discuss how control over magnetism is achieved through these functional antiferrodistortive octahedron rotations.
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