Physicists harness effects of disorder in magnetic sensors

September 9, 2008,
University of Chicago physicist Thomas Rosenbaum, with the helium dilution refrigerator in his laboratory, where he observes the quantum behavior of materials chilled to temperatures approaching absolute zero. (Photo: Dan Dry)

(PhysOrg.com) -- University of Chicago scientists have discovered how to make magnetic sensors capable of operating at the high temperatures that ceramic engines in cars and aircraft of the future will require for higher operating efficiency than today's internal combustion technology.

The key to fabricating the sensors involves slightly diluting samples of a well-known semiconductor material, called indium antimonide, which is valued for its purity. Chicago's Thomas Rosenbaum and associate Jingshi Hu, now of the Massachusetts Institute of Technology, have published their formula in the September issue of the journal Nature Materials.

Most magnetic sensors operate by detecting how a magnetic field alters the path of an electron. Conventional sensors lose this capability when subjected to temperatures reaching hundreds of degrees. Not so in the indium antimonide magnetosensors that Rosenbaum and Hu developed with support from the U.S. Department of Energy.

"This sensor would be able to function in those sorts of temperatures without any degradation," said Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics.

Rosenbaum's research typically focuses on the properties of materials observed at the atomic level when subjected to temperatures near absolute zero (minus-460 degrees Fahrenheit). More than a decade ago, he led a team of scientists in experiments involving silver selenide and silver telluride, two materials that exhibited no magnetic response at low temperatures. But when the team introduced a tiny amount of silver (one part in 10,000) to the materials, their magnetic response skyrocketed.

In silver selenide and silver telluride, the magnetic response disappears at room temperature, which limits their technological applications. But Rosenbaum and Hu now have used two methods to recreate the effect at much higher temperatures in indium antimonide. Disordering the material—simply grinding it up and fusing it with heat—produces the effect. So does introducing impurities of just a few parts per million.

"What's nice about it is that, first, it's an unexpected phenomenon; and second, it's a very useful one," said University of Cambridge physicist Peter Littlewood. "Normally, in order to make large effects, you have to have pure samples."

Before Rosenbaum and Hu's latest experiments, two theories dueled to explain the effect. In 2003, Littlewood and Meera Paris, now a postdoctoral fellow at the Princeton Center for Theoretical Physics, explained the effect using classical physics, the laws of nature that govern physics above the atomic scale. Nobel laureate Alexei Abrikosov of Argonne National Laboratory devised an explanation based on quantum physics, the dominant physics at ultrasmall scales.

"We've shown that both theories work, just in different regimes," Rosenbaum said.

Littlewood lauded the sequence of events as an example of how science ought to work. "There's a discovery of a result. There's a theory about it. Further experiments are done to test the theory. They work and that provokes another idea, and you bounce to and fro," Littlewood said. "That's how we like to describe science progressing. One is rarely lucky enough to do that over a long period."

Provided by University of Chicago

Explore further: Scientists reach milestone in study of emergent magnetism

Related Stories

New magnetic tuning method enhances data storage

February 9, 2010

Researchers in Chicago and London have developed a method for controlling the properties of magnets that could be used to improve the storage capacity of next-generation computer hard drives.

Manipulating quantum order

November 17, 2016

Cool a material to sufficiently low temperatures and it will seek some form of collective order. Add quantum mechanics or confine the geometry and the states of matter that emerge can be exotic, including electrons whose ...

Caltech announces discovery in fundamental physics

August 10, 2015

When the transistor was invented in 1947 at Bell Labs, few could have foreseen the future impact of the device. This fundamental development in science and engineering was critical to the invention of handheld radios, led ...

Recommended for you

Pattern formation—the paradoxical role of turbulence

February 19, 2018

The formation of self-organizing molecular patterns in cells is a critical component of many biological processes. Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich have proposed a new theory to explain how ...

Bringing a hidden superconducting state to light

February 16, 2018

A team of scientists has detected a hidden state of electronic order in a layered material containing lanthanum, barium, copper, and oxygen (LBCO). When cooled to a certain temperature and with certain concentrations of barium, ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

dconine
not rated yet Sep 13, 2008
Too bad we can't get this kind of cooperation on cold fusion anomalies......

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.