Multiferroics—materials that exhibit both magnetic and electric order—are of interest for next-generation computing, but are difficult to create because the conditions conducive to each of those states are usually mutually exclusive. In most multiferroics found to date, their respective properties emerge only at extremely low temperatures.

Two years ago, researchers in the labs of Darrell Schlom, Cornell University professor of industrial chemistry, and Dan Ralph, Cornell professor of physics—in collaboration with Ramamoorthy Ramesh, professor of materials science and engineering at the University of California, Berkeley—published a paper announcing a breakthrough in multiferroics involving the only known material in which magnetism can be controlled by applying an electric field at room temperature: the multiferroic bismuth ferrite.

The magnetoelectric multiferroic: the double strand of purple represents the extra layer of iron oxide, which makes it a multiferroic at near room temperature. Image credit: Emily Ryan, Megan Holtz.Schlom’s group has now partnered with David Muller and Craig Fennie, Cornell professors of applied and engineering physics, to take that research a step further. The researchers have combined two non-multiferroic materials, using the best attributes of each to create a new room-temperature multiferroic.

The group engineered thin films of hexagonal lutetium iron oxide (LuFeO3), a material known to be a robust ferroelectric but not strongly magnetic. The LuFeO3 consists of alternating single monolayers of lutetium oxide and iron oxide.

The researchers found that they could combine these two materials at the atomic scale to create a new compound that was not only multiferroic, but had better properties than either of the individual constituents. They discovered that they needed to add just one extra monolayer of iron oxide to every 10 atomic repeats of the LuFeO3 to dramatically change the properties of the system.

That precision engineering was done via molecular-beam epitaxy (MBE). A technique Schlom likens to “atomic spray painting,” MBE let the researchers design and assemble the two different materials in layers, a single atom at a time.

The combination of the two materials produced a strongly ferrimagnetic layer near room temperature. They then tested the new material to show that the ferrimagnetic atoms followed the alignment of their ferroelectric neighbors when switched by an electric field.

In electronic devices, the advantages of multiferroics include their reversible polarization in response to low-power electric fields—as opposed to heat-generating and power-sapping electrical currents—and their ability to hold their polarized state without the need for continuous power. High-performance memory chips make use of ferroelectric or ferromagnetic materials.

“Our work shows that an entirely different mechanism is active in this new material,” Schlom says, “giving us hope for even better—higher-temperature and stronger—multiferroics for the future.”