Defect-engineered ferroelectricity and magnetoelectric coupling in LaFeO₃ thin films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Single-phase multiferroics operating at room temperature are highly sought after but challenging to create.
• Lanthanum ferrite (LaFeO₃), a bulk antiferromagnet, typically lacks ferroelectric properties.
• Existing materials often exhibit mutually exclusive ferroelectric and magnetic behaviors.

Purpose of the Study:

• To engineer room-temperature ferroelectricity in lanthanum ferrite (LFO) thin films.
• To investigate the role of defect engineering in inducing multiferroic properties.
• To establish a general strategy for designing multifunctional rare earth orthoferrites.

Main Methods:

• Epitaxial thin film growth of LFO with controlled oxygen partial pressure.
• Deliberate introduction of cationic off-stoichiometry and antisite defects (La_Fe and Fe_La).
• Characterization using scanning transmission electron microscopy (STEM), positive-up-negative-down (PUND) measurements, and density functional theory (DFT) calculations.
• Investigation of magnetoelectric coupling using piezoresponse force microscopy (PFM) under magnetic fields.

Main Results:

• Successful creation of room-temperature ferroelectricity in epitaxial LFO thin films.
• Identification of La_Fe and Fe_La antisite defects as the origin of the polar R3c phase.
• Confirmation of intrinsic switchable ferroelectricity attributed to these defects.
• Observation of significant magnetoelectric coupling.

Conclusions:

• Cationic antisite defect engineering is a novel mechanism for activating multiferroicity in LFO.
• This defect-engineering strategy provides a general paradigm for designing multifunctional properties in rare earth orthoferrites.
• The findings pave the way for developing new room-temperature multiferroic materials for advanced applications.