Training the Polarization in Integrated La_0.15 Bi_0.85 FeO₃ -Based Devices

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Magnetoelectric multiferroic heterostructures, particularly those based on bismuth ferrite (BiFeO3), are critical for voltage-controlled magnetic switching.
• Controlling ferroelectric domains and net in-plane polarization is key to their functionality.
• Chemical substitution in BiFeO3 aims to reduce energy dissipation but often leads to domain disorder.

Purpose of the Study:

• To investigate the impact of heavy lanthanum (La) substitution on the domain configuration and net in-plane polarization of BiFeO3 films.
• To determine if the imprinted in-plane polarization in disordered films can be manipulated.
• To assess the potential for integrating these modified materials into energy-efficient devices.

Main Methods:

• Non-invasive optical second-harmonic generation microscopy was used to analyze heavily La-substituted BiFeO3 films.
• Operando studies were performed on capacitor heterostructures incorporating these films.
• Out-of-plane electric fields were applied to train the ferroelectric domains and polarization.

Main Results:

• Despite apparent domain disorder from La substitution, a weak net in-plane polarization persists in pristine BiFeO3 films.
• This ingrained polarization is trainable using accessible out-of-plane electric fields.
• Post-treatment in capacitor heterostructures led to full domain configuration restoration and a significant enhancement of net in-plane polarization.

Conclusions:

• The net in-plane polarization of BiFeO3 exhibits remarkable robustness against chemical modification, even with induced domain disorder.
• The ability to train and enhance this polarization offers a pathway for practical applications.
• These findings are vital for the development of energy-efficient magnetoelectric devices.