Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Nanophysicists find unexpected magnetic effect

Kondo effect noted in single-atom contacts of pure ferromagnets

Spanish and U.S. physicists studying nanoelectronics have found that size really does matter when it comes to predicting the behavior of electrical contacts that are just one atom wide.

In new research appearing this week in the journal Nature, physicists at Spain's University of Alicante and at Rice University in Houston have found that single-atom contacts made of ferromagnetic metals like iron, cobalt and nickel behave very differently than do slightly larger versions that are on the order of the devices used in today's electronic gadgets.

"We've found that the last atom in the line, the one out there on the very end, doesn't want to align itself and behave like we expect it to," said study co-author Doug Natelson, associate professor of physics and astronomy at Rice. "What this shows is that you can really alter what you think of as a defining property of these metals just by reducing their size."

The findings center on the "Kondo effect," one of the most studied and well documented phenomena in magnetic materials. Scientists learned early in the study of electromagnetism that normal metals, like copper, conduct electricity better as they became colder. But in the 1930s, scientists found that adding even trace amounts of ferromagnetic metals like iron would throw off this effect. In the 1960s, Japanese physicist Jun Kondo explained the effect: while cooling normal metals results in fewer vibrations among atoms, and thus less electrical resistance, mobile electrons in the metals tend to align their spins in the opposite direction of the spins of electrons in a magnetic atom. Thus, at low temperatures, an electron moving past a magnetic impurity will tend to flip its spin and therefore get deflected from its path. This explains why even tiny magnetic impurities can cause electrical resistance to rise, in spite of further cooling.

Based on decades of experimental evidence, physicists would not ordinarily expect the Kondo effect to play a role in wires and contacts made entirely of ferromagnetic metals like iron, cobalt and nickel. Yet that is precisely what co-authors Maria Reyes Calvo and Carlos Untiedt found occurring in experiments in Untiedt's laboratory in Alicante, Spain, in 2008. Calvo, a graduate student, was working with single-atom ferromagnetic contacts that were created by lowering and raising the tip of a scanning tunneling microscope onto a surface.

Untiedt knew that Natelson worked on similar-sized systems that were created in a wholly different way, by laying down metals on a flat surface. So Untiedt arranged for a travel grant from the Spanish government and Natelson agreed to oversee Calvo's recreation of the study at Rice.

"Reyes was a very quick study, and within just a few weeks she had mastered our technique for making single-atom junctions," Natelson said. "She conducted dozens of experiments on junctions made of cobalt and nickel, and we saw the characteristic Kondo effect in the conductance, just as she had seen in Spain."

Co-authors Joaquín Fernández-Rossier and Juan José Palacios, both of the University of Alicante, and David Jacob of Rutgers University. provided a theoretical framework to help explain the unexpected effect. Natelson said the team's discovery is yet another example of the unique types of effects that characterize nanotechnology.

"The fact that this atom is all by itself at the surface is what makes it behave so differently, and it shows that engineers need to be mindful of surface effects in anything they design at this level," Natelson said.

The research was supported by the European Union's Seventh Framework Program, the National Science Foundation, the Packard Foundation and the W.M. Keck Foundation.

Jade Boyd | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>