November 19, 2013

The Scientist: Prof. Craig Fennie Builds New Materials From Scratch

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By EMMA JOHNSTON

Try to imagine a material that does not exist. It is one thing to decide what properties you want in the new material, but to bring the material into reality is no simple task.

One Cornell professor is working on doing exactly that. Prof. Craig Fennie, applied and engineering physics, designs new materials called multiferroics which have both ferroelectric and ferromagnetic characteristics.

Ferromagnetism involves the spontaneous alignment of magnetic dipoles in an object which originate from electron spin, according to Fennie. This realignment leads to spontaneous magnetization.

One example of this is the creation of permanent magnets from materials such as iron.

Ferroelectricity is the electric version of ferromagnetism. Materials with ferroelectric properties have electric dipoles that spontaneously align to produce electric polarization.

“These are materials that you can apply an electric field or a magnetic field to and they will respond in some useful way,” Fennie said.

Ferroelectric materials have the added property that their electric behavior can be turned on and off externally. This property could potentially be utilized in new computing devices, Fennie said.

“[Ferroelectric materials] are just very rare, and the ones that do exist have been boring, so there’s been a huge effort in the last ten years to try to create more useful materials like this,” he said.

Although Fennie has discovered several transition metal oxides with ferroelectric properties, he said that finding new materials with these characteristics is not a simple task.

“That’s the heart of it; that’s the creative part,” Fennie said. “That’s the thing that’s not an algorithm, it’s hard to teach. It’s very much driven by intuition.”

According to Fennie, in physics research, people typically look at something that already exists and then study its properties.

Fennie and his research team, however, do this in reverse. Fennie will start with a model that can describe a desired property. Fennie said that he then thinks about what it would take to realize that property in a real material.

“Then we start building that material atom by atom,” Fennie said.

Once the material has been created, Fennie’s lab tests whether or not it actually exhibits the properties it theoretically has. Fennie pioneered this procedure which he calls a “first principles quantum mechanical calculation.”

Fennie also works with Mott insulators, materials that act as both conductors and insulators depending on certain conditions.

By applying a small voltage, for example, you could turn the conducting properties of the new material on and the insulator properties off.

“As soon as you can make a transistor, or an on-off switch, you can make a computing device,” Fennie said.

Fennie recently began to work with Cornell’s Energy Materials Center which aims to “advance the science of energy conversion and storage by exploiting fundamental properties of active materials,” according to its website. At the Energy Materials Center, Fennie researches ways in which photocatalytic chemicals, or chemicals that speed reactions when exposed to light, can be used in solar fuel cells.

“Moving in these new directions, I don’t have the same knowledge that I have in the area I’ve been working in the past five years. So it’s a bit scary, but at the same time it’s like, what can we do that’s really different? And I like doing things that are different,” Fennie said.

To reward and encourage his innovative techniques and creation of new materials, Fennie was recently awarded one of the 2013 MacArthur Fellowships, known colloquially as “genius grants.”

“I don’t like following fads in science, and there are lots of fads in science. There’s a topic that then everyone flocks after and tries to work on see who can be first to get out their paper,” Fennie said. “But science isn’t about a rush to see who can be first to get out a paper. If you’re going to do something that’s really meaningful then it means that no one else is probably thinking about it. And that’s what I love.”

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