Large Enhancement of Properties in Strained Lead-free Multiferroic Solid Solutions with Strong Deviation from Vegard's Law

TL;DR

This study demonstrates that strain engineering combined with chemical doping in epitaxial films of BiFeO3 BaTiO3 significantly enhances multiferroic properties and deviates from Vegard's law, surpassing bulk material capabilities.

Contribution

It reveals a novel approach to enhance multiferroic properties in lead-free films by leveraging strain and doping, breaking Vegard's law constraints.

Findings

Significant deviation from Vegard's law in strained films

Enhanced multiferroic properties including magnetization and polarization

Superior ferroelectricity compared to bulk materials

Abstract

Efforts to combine the advantages of multiple systems to enhance functionlities through solid solution design present a great challenge due to the constraint imposed by the classical Vegard law. Here, we successfully navigate this trade off by leveraging the synergistic effect of chemical doping and strain engineering in solid solution system of BiFeO3 BaTiO3. Unlike bulks, a significant deviation from the Vegard law accompanying with enhanced multiferroism is observed in the strained solid solution epitaxial films, where we achieve a pronounced tetragonality, enhanced saturated magnetization, substantial polarization, high ferroelectric Curie temperature, all while maintaining impressively low leakage current. These characteristics surpass the properties of their parent BiFeO3 and BaTiO3 films. Moreover, the superior ferroelectricity has never been reported in corresponding bulks. These findings underscore the potential of strained BiFeO3 BaTiO3 films as lead-free, room-temperature multiferroics.