A boring material, "stretched", could lead to an electronics revolutionBy Jared Sagoff • October 1, 2010
The oxide compound europium titanate is fairly boring on its own, but sliced nanometers thin and chemically stretched on a specially-designed template, it takes on properties that could revolutionize the electronics industry, according to research carried out at the U.S. Department of Energy’s Advanced Photon Source (APS) at Argonne National Laboratory.
A research team from Cornell University, publishing in the journal Nature, reported that thin films of europium titanate (EuTiO3) become both ferroelectric (electrically polarized) and ferromagnetic (exhibiting a permanent magnetic field) when stretched across a substrate of dysprosium scandate, another type of oxide. The best simultaneously ferroelectric and ferromagnetic material now known pales in comparison by a factor of 1,000.
"Materials by design" is an exciting new area at the confluence of advanced theory of materials and novel synthesis approaches. In the area of new magnetic materials, one of the exciting topics is materials that simultaneously show spontaneous electric and magnetic order, known as multiferroics. However, in most cases a material has either strong electric or magnetic order while the other order is quite weak.
Simultaneous ferroelectricity and ferromagnetism is rare in nature and coveted by electronics visionaries. A material with this combination could form the basis for a wide range of innovative technologies.
Previous studies searched directly for a ferromagnetic ferroelectric -- an extremely rare form of matter. The researchers in this study used first-principles theory to look among materials that are neither ferromagnetic nor ferroelectric, of which there are many, and to identify candidates that, when squeezed or stretched, take on these properties.
This strategy, demonstrated using the europium titanate, opens the door to other ferromagnetic ferroelectrics that may work at even higher temperatures using this same materials-by-design strategy and could be a key step toward the development of next-generation memory storage, superb magnetic field sensors, and many other applications long dreamed about.
The Cornell experiment was conducted at an extremely cold temperature: about 4Â° Kelvin (-452 Â° Fahrenheit). The team is already working on materials that are predicted to show such properties at much higher temperatures.
REFERENCE: June Hyuk Lee et al. Nature 466, 954 (19 August 2010). DOI:10.1038/nature09331.