Brown University Engineers Eliminate Dead Layer in Multiferroic Materials
Researchers at Brown University have developed a fabrication technique that eliminates the “dead layer” effect in bismuth ferrite, allowing ultrathin multiferroic films down to a few angstroms to retain their ferroelectric and magnetic properties. Published in Nature Materials on October 28, 2026, the breakthrough addresses a longstanding obstacle that previously caused materials to lose their electrical and magnetic functionality when scaled down for computer chips.
Compressive Strain and Metallic Screening Overcome Scaling Limits
When multiferroic films become extremely thin, atomic structure shifts and internal electric fields typically destabilize polarization, destroying the behavior required for electronic applications. To combat this degradation, the Brown research team grew bismuth ferrite on dysprosium scandate, a rare earth-based crystalline substrate with a smaller lattice spacing. This lattice mismatch places the film under compressive strain to preserve its atomic arrangement. Additionally, the researchers incorporated a metallic layer that screens unwanted electric fields, preventing them from disrupting polarization. By controlling both factors, the team maintained bismuth ferrite functionality at thicknesses measuring only a few angstroms, or roughly four billionths of an inch.
Altermagnetism Emerges in Ultrathin Bismuth Ferrite Films
Beyond preserving standard multiferroic characteristics, the engineered three-layer structure induces an additional magnetic state known as altermagnetism. Lucas Caretta, an assistant professor of engineering at Brown who led the work, noted that while ferromagnets produce strong signals that are easy to read, they operate relatively slowly and create stray magnetic fields that hinder dense device integration. Antiferromagnets avoid stray fields and operate faster, but their signals remain difficult to detect. Altermagnets combine these traits by enabling fast operation, dense integration, and strong electrical signals for data readout.
Federal and Institutional Backing Funds Advanced Microchip Materials
The study detailing these findings builds on bulk material properties to engineer structures potentially better suited for computing demands driven by artificial intelligence. Funding for the research was provided by the U.S. Army Research Office under grant W911NF-21-2-0162, the National Science Foundation under grants DMR-2039380 and OIA-2327352, and the U.S. Department of Energy under grant DE-AC02-05CH11231.
Frequently Asked Questions About Ultrathin Bismuth Ferrite Research
How does the dysprosium scandate substrate affect the bismuth ferrite film?
Dysprosium scandate possesses a crystalline structure with a narrower lattice spacing than bismuth ferrite. This mismatch places compressive strain on the bismuth ferrite layer, helping to maintain the functional atomic arrangement required for its electrical and magnetic properties.
What specific funding agencies supported the October 2026 study?
The research published in Nature Materials received financial backing from the U.S. Army Research Office, the National Science Foundation, and the U.S. Department of Energy.
What precise thickness did the Brown University team achieve while keeping the material functional?
The researchers successfully maintained ferroelectric and magnetic behavior in bismuth ferrite films scaled down to a thickness of only a few angstroms.
“We know the underlying properties are already there in the bulk materials,” Caretta said. “The trick is learning how to engineer them into a form that’s useful — and sometimes even better than what nature gives us.”
Keep reading