The Scientist: Professor Greg Fuchs Looks at Magnetic Moments on the Nanoscale

February 26, 2014 1:00 am0 comments

By IAN MACCORMACK

The physical world at the nanoscale is full of rich phenomena. Understanding and taking advantage of the physics of these tiny systems promises a multitude of advancements in the development of technology, according to Prof. Gregory Fuchs Ph.D. ’07, applied and engineering physics. The only problem is that nano-scale systems are extremely hard to see.

Fuchs seeks to make this world more accessible. His research group is developing methods to create small-scale images of the relative direction of a magnet’s north pole to its south pole, known as its magnetic moment. The magnetic moment determines both the direction and strength of the resulting magnetic field, according to Fuchs.

Prof. Greg Fuchs

Prof. Greg Fuchs

“[We are] trying to find ways to image — literally take pictures — of magnetization dynamically. So not just a static picture,” Fuchs said. “We want to take a picture of the magnetic moment on the correct fundamental scale, both in space and in time.”

The challenge, according to Fuchs, is rooted in the sheer tiny size of individual magnetic moments, and the rate at which they change.

This means that the device they use to look at the magnetic moments must be a high enough resolution to focus on extremely small areas.

“Taking a picture at these scales is really hard, and I can tell you right now that we haven’t done that yet,” Fuchs said.

Currently, techniques for this kind of magnetic imaging do exist, using a method involving what is called XMCD, or X-ray magnetic circular dichroism. However, XMCD techniques involve the use of very high energy X-rays, which can only be produced by a particle accelerator, according to Fuchs.

“In order to use that technique, unfortunately, you have to go to a synchrotron. It’s a facility-anchored experiment. My hope is to be able to do this with things that you can put on a table,” Fuchs said.

Fuchs and his group have been developing methods for surmounting this challenge. He is exploiting what is called the Anomalous Nernst Effect — a phenomenon in which an electricity-conducting material is subjected to a particular set of conditions, notably a high temperature at a small point.

This generates a small voltage, which provides information about the size and orientation of the magnetic moment. This information corresponds to an image on film, which is laid parallel to the experiment.

“What we do now is use a laser to warm up a region,” Fuchs said, “and then we use electrical pickups to pick up this small voltage. If we can figure out ways to heat a smaller region, then we can increase the resolution. That’s the basic idea of our magnetics research.”

Once fully developed, the Fuchs group’s methods for imaging magnetization will be an invaluable utility for creating new technology.

“We’re not working towards a really direct application … there isn’t a device,” Fuchs said. “Instead it’s a tool. If you have this tool, you can start to answer questions you couldn’t ask before, which is really useful in the development of technology.”

The ability to view magnetization at a small scale will open new doors in information processing and a variety of other fields, according to Fuchs.

For his innovative research in the area of magnetism, the Department of Defense awarded Fuchs the Presidential Early Career Award for Scientists and Engineers. The awards are given annually at a ceremony in Washington D.C. for outstanding contributions to scientific research.

In addition to his work in magnetism, Fuchs has other areas of inquiry.

“The theme of my research is individual nanoscale systems. Either spin or electronic systems – isolated ones,” Fuchs said.

His other areas of research have potential applications in electronic sensing, solar power, information storage, and more.

“Everything is an interesting problem,” Fuchs said. “Everything that I have actually gotten involved in, I have found exciting. It’s the enthusiasm that keeps you going forward. Then things just happen from there.”

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