Manipulation of Ferroic Orders via Continuous Biaxial Strain Engineering in Multiferroic Bismuth Ferrite.

Continuous strain engineering of multiferroics not only enhances understanding of their properties but also guides the optimization of their performances for use in electronic, optical, and magnetic devices. However, due to technical challenges in real-time monitoring of the ferroic orders, the precise evolution process remains unclear. Here, the evolution of the ferroelectric (FE) and antiferromagnetic (AFM) orders are revealed in multiferroic freestanding BiFeO films under sequential and anisotropic biaxial strain, using rotational anisotropy second harmonic generation (RA-SHG) technology and first-principles calculations.

Latent Electronic (Anti-)Ferroelectricity in BiNiO_{3}.

BiNiO_{3} exhibits an unusual metal-insulator transition from Pnma to P1[over ¯] that is related to charge ordering at the Bi sites, which is intriguingly distinct from the charge ordering at Ni sites usually observed in related rare-earth nickelates. Here, using first principles calculations, we first rationalize the phase transition from Pnma to P1[over ¯], revealing an overlooked intermediate P2_{1}/m bridging phase and a complex interplay between distinct degrees of freedom. Going further, we point out that the charge ordering at Bi sites in the P1[over ¯] phase is not unique.