Assistant Professor of Physics
Kirill Belashchenko | University of Nebraska, Lincoln
A New Kind of Spin Doctor
Kirill Belashchenko sees more to magnets and spin than just MP3s and iPods. He works on new theory that may lead to spin-based devices that will be faster than ever at reading and analyzing data.
For a moment, imagine that you are in his classroom at the University of Nebraska as he explains:
Zero temperature, or absolute zero, is the lowest possible temperature (about minus 273 degrees Celsius), at which any system is in its ground quantum-mechanical state. At finite (non-zero) temperatures, thermal excitations become important. "But practically we are talking about temperatures of the order of the magnetic transition temperature," he adds. For example, iron has a Curie point of roughly 1043 Kelvin (770 degrees C); magnetization decreases continuously as iron is heated and reaches zero at 1043 K.
Here's the good news.
Belashchenko aims to come up with a new technique to study magnetic materials, at finite temperatures (aren't you glad he explained that?). "It's one thing to study how materials conduct current at absolute zero," he says. "At room temperatures, or higher, you need to do something different." And Belashchenko says he intends to do just that.
To be exact, he aims to design first-principles techniques to describe the magnetic, electronic, and transport properties of magnetic materials, like iron, at temperatures starting from absolute zero and up to the Curie point. "First principles" means they start from fundamental quantum equations and use the so-called "density functional theory.
As a member of the prestigious Nebraska Center for Materials and Nanoscience, Belashchenko focuses on the theory needed for computers that use spintronics, which is based on quantum spin of electrons rather than charge.
Breakthroughs in that area of nanotechnology won the Nobel Prize in physics in 2007. Two scientists discovered an effect called giant magnetoresistance, or GMR, for the big changes in electrical resistance that are linked to small changes in a magnetic field. The discovery has made possible MP3s and other devices to store data or video appearing since the late 1990s.
Belashchenko's work may play a role in the design of smaller, denser memory storage devices that use electron spin in scanning heads that are no thicker than a few nanometers, or billionths of a meter. But many questions remain about how magnetic fields affect the flow of current -- or resistance -- in materials, especially iron and other magnetic metals, or ferromagnets.
"This has fundamental importance and applications for spintronics," he says. "We hope we can design new devices based on spin, to replace transistors in information processing. Many people are talking about spintronic computers taking less power and working faster. But it's very far off. No one even knows if it will possible. It's very early in the research."
Another of his research themes involves an effect called tunnel magnetoresistance, which may be a key to future memories for computers. In such memory units, the bits of information are nonvolatile, and do not disappear with the power off.
Feasible? "No one knows yet," he said, "but everyone is talking about it."
Finding more sensitive ways to process information, moving beyond data storage and retrieval, would be very valuable, he says. But there are many challenges. Which architectures will best suit the design of spintronic components? How can you design a cascade to work as a transistor circuit? "We have ideas and models for pieces of the puzzle, but not for the whole puzzle," he said. "Nothing you can use today with natural materials."
As he continues teaching Nebraska's core courses in graduate quantum mechanics and statistical physics, he and his team will be looking for ways to describe the electronic structure of magnetic materials, "with as few approximations as possible."
Belashchenko studied at the Institute of Steel and Alloys in Moscow, took a Ph.D. at the Kurchatov Institute and spent three years at the Ames Lab, a U.S. Department of Energy site in Iowa.
Teaching Component
The teaching part of his 2008 Cottrell Award honors his proposal to assess students' progress and coordinate curriculum in ways that will ensure more consistency of concepts across all classes in his department at Nebraska. "We shouldn't just assume that students know certain things," he said. "The assessments will tell us how well they are actually doing and help us teach better."
And all of that ought to keep him busy the next few football seasons. He's never been to a game, preferring to work in his warm office on those afternoons when the football fans in the stadium are complaining that it feels like absolute zero.
