Deterministic and robust room-temperature exchange coupling in monodomain multiferroic BiFeO₃ heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Multiferroic BiFeO3 thin films are crucial for spintronic devices, requiring precise control of magnetoelectric and exchange coupling.
• Existing methods rely on multi-step ferroelectric switching, which can lead to issues with domain walls, fatigue, and device reproducibility.
• A monodomain state with single-step switching offers a more robust and scalable alternative for device applications.

Purpose of the Study:

• To demonstrate deterministic and robust exchange coupling between monodomain BiFeO3 films and a cobalt (Co) overlayer at room temperature.
• To investigate an alternative approach to spintronic device control that avoids domain wall complexities.
• To establish a foundation for practical, low-power non-volatile magnetoelectric devices.

Main Methods:

• Fabrication of monodomain BiFeO3 thin films.
• Integration with a ferromagnetic cobalt overlayer.
• Characterization of the magnetoelectric coupling and exchange interaction via magnetic moment rotation measurements.

Main Results:

• Demonstrated intrinsic, room-temperature exchange coupling between monodomain BiFeO3 and Co overlayer, independent of domain walls.
• Observed deterministic and robust ~90° in-plane Co moment rotation upon single-step ferroelectric switching.
• Achieved reproducible switching behavior over hundreds of cycles, highlighting device stability.

Conclusions:

• Single-step switching in monodomain BiFeO3 enables robust control of coupled magnetization.
• This approach overcomes limitations associated with domain walls in previous multiferroic spintronic device designs.
• The findings pave the way for developing efficient, low-power, non-volatile magnetoelectric memory and logic devices.