Multiferroic Domain Dynamics in Strained Strontium Titanate

TL;DR

This study demonstrates how biaxial strain induces multiferroic phases in strontium titanate, revealing domain dynamics and switching mechanisms through combined experimental and theoretical approaches.

Contribution

It provides new insights into strain-induced multiferroicity in SrTiO3, including domain imaging, phase transitions, and switching mechanisms validated by theory.

Findings

Strain induces a transition to a ferroelectric phase in SrTiO3.

Domain switching occurs via coupled 90-degree ferroelectric-ferroelastic wall motion.

Results align with first-principles and phase-field predictions.

Abstract

Multiferroicity can be induced in strontium titanate by applying biaxial strain, resulting in the coexistence of both ferroelectric and antiferrodistortive domains. The magnitude and sign of the strain imposed on the lattice by design can be used to tune the phase transitions and interactions between these two phenomena. Using optical second harmonic generation, we report a transition from centrosymmetric 4/mmm phase to ferroelectric mm2, followed by an antiferrodistortive transition to a coupled ferroelastic-ferroelectric mm2 phase in a strontium titanate thin film strained in biaxial tension by 0.94%. The results agree well with theoretical first principles and phase-field predictions. Direct imaging of domains arising from the ferroelectric phase transition, and its switching under electric fields is demonstrated using piezoelectric force microscopy. Nonlinear optics combined with phase-field modeling is used to show that the dominant multiferroic domain switching mechanism is through coupled 90 degree ferroelectric-ferroelastic domain wall motion. More broadly, these studies of coexisting ferroelectric (polar) and antiferrodistortive rotation (axial) phenomena could have relevance to multiferroics with coexisting ferroelectric (polar) and magnetic (axial) phenomena.