Universal Polar Instability in Highly Orthorhombic Perovskites

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• Designing multiferroic ABO3 perovskites is challenging due to magnetic cations and antiferrodistortive modes suppressing polar distortions.
• Existing magnetic perovskites often lack the necessary symmetry for multiferroic applications.

Purpose of the Study:

• To investigate mechanisms enabling polar distortions in magnetic perovskites.
• To identify novel multiferroic materials with desirable properties.

Main Methods:

• First-principles simulations were employed to study free energy invariants.
• Analysis focused on quadlinear and trilinear couplings between structural modes.

Main Results:

• Quadlinear and trilinear invariants drive an avalanche-like transition to non-centrosymmetric Pna21 symmetry in magnetic perovskites.
• Tensile epitaxial strain favors the Pna21 phase, inducing out-of-plane polarization.
• This mechanism predicts numerous novel multiferroics with tunable magnetoelectric properties.

Conclusions:

• Specific free energy invariants can overcome restrictions hindering multiferroicity in ABO3 perovskites.
• Strain engineering is a viable route to achieve useful polarization in these materials.
• The identified mechanism opens pathways for designing advanced multiferroic materials.