Strain-Induced Antiferroelectric–Ferroelectric–Antiferroelectric Phase Transitions in Epitaxial LaTaO₄ Films

Abstract

We employed first-principles to delve into the straininduced structural phase transitions in epitaxial LaTaO 4 films. The ground state of bulk LaTaO 4 adopts a monoclinic antiferroelectric phase, characterized by the antiphase rotation of two adjacent oxygen octahedra layers. Under epitaxial tensile strain, LaTaO 4 thin films undergo a consecutive phase transition, namely, antiferroelectric− ferroelectric−antiferroelectric phase transitions. The ferroelectricity in the orthorhombic phase under tensile strain originates from the inphase rotation of two adjacent oxygen octahedra layers, in contrast to the case of perovskite systems, in which octahedra rotation suppresses the conventional proper ferroelectricity. With spin−orbit coupling effects, a pronounced Rashba effect at the Brillouin zone center naturally leads to the formation of opposite directions of spin texture. Moreover, the tensile strain also synergistically enhances the corresponding Rashba parameters. Our findings may provide novel insights for controlling oxygen octahedra rotation to achieve control over the ferroelectricity and Rashba effect, which holds promising implications for applications in electronics and spintronics.