Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

At Small Scales, Tug-of-War Between Electrons Can Lead to Magnetism Under Surprising Circumstances

30.06.2011
At the smallest scales, magnetism may not work quite the way scientists expected, according to a recent paper in Physical Review Letters by Rafal Oszwaldowski and Igor Zutic of the University at Buffalo and Andre Petukhov of the South Dakota School of Mines and Technology.

The three physicists have proposed that it would be possible to create a quantum dot -- a kind of nanoparticle -- that is magnetic under surprising circumstances.

Magnetism is determined by a property all electrons possess: spin. Individual spins are akin to tiny bar magnets, which have north and south poles. Electrons can have an "up" or "down" spin, and a material is magnetic when most of its electrons have the same spin.

Mobile electrons can act as "magnetic messengers," using their own spin to align the spins of nearby atoms. If two mobile electrons with opposite spins are in an area, conventional wisdom says that their influences should cancel out, leaving a material without magnetic properties.

But the UB-South Dakota team has proposed that at very small scales, magnetism may be more nuanced than that. It is possible, the physicists say, to observe a peculiar form of magnetism in quantum dots whose mobile electrons have opposing spins.

In their Physical Review Letters article, the researchers describe a theoretical scenario involving a quantum dot that contains two free-floating, mobile electrons with opposite spins, along with manganese atoms fixed at precise locations within the quantum dot.

The quantum dot's mobile electrons act as "magnetic messengers," using their own spins to align the spins of nearby manganese atoms.

Under these circumstances, conventional thinking would predict a stalemate: Each mobile electron exerts an equal influence over spins of manganese atoms, so neither is able to "win."

Through complex calculations, however, Oszwaldowski, Zutic and Petukhov show that the quantum dot's two mobile electrons will actually influence the manganese spins differently.

That's because while one mobile electron prefers to stay in the middle of the quantum dot, the other prefers to locate further toward the edges. As a result, manganese atoms in different parts of the quantum dot receive different messages about which way to align their spins.

In the "tug-of-war" that ensues, the mobile electron that interacts more intensely with the manganese atoms "wins," aligning more spins and causing the quantum dot, as a whole, to be magnetic. (For a visual representation of this tug-of-war, see Figure 1.)

This prediction, if proven, could "completely alter the basic notions that we have about magnetic interactions," Zutic says.

"When you have two mobile electrons with opposite spins, the assumption is that there is a nice balance of up and down spins, and therefore, there is no magnetic message, or nothing that could be sent to align nearby manganese spins," he says. "But what we are saying is that it is actually a tug of war. The building blocks of magnetism are still mysterious and hold many surprises."

Scientists including UB Professor Athos Petrou, UB College of Arts and Sciences Dean Bruce McCombe and UB Vice President for Research Alexander Cartwright have demonstrated experimentally that in a quantum dot with just one mobile electron, the mobile electron will act as a magnetic messenger, robustly aligning the spins of adjacent manganese atoms.

Now, Petrou and his collaborators are interested in taking their research a step further and testing the tug-of-war prediction for two-electron quantum dots, Zutic says.

Zutic adds that learning more about magnetism is important as society continues to find novel uses for magnets, which could advance technologies including lasers, medical imaging devices and, importantly, computers.

He explains the promise of magnet- or spin-based computing technology -- called "spintronics" -- by contrasting it with conventional electronics. Modern, electronic gadgets record and read data as a blueprint of ones and zeros that are represented, in circuits, by the presence or absence of electrons. Processing information requires moving electrons, which consumes energy and produces heat.

Spintronic gadgets, in contrast, store and process data by exploiting electrons' "up" and "down" spins, which can stand for the ones and zeros devices read. Future energy-saving improvements in data processing could include devices that process information by "flipping" spin instead of shuttling electrons around.

Studying how magnetism works on a small scale is particularly important, Zutic says, because "we would like to pack more information into less space."

And, of course, unraveling the mysteries of magnetism is satisfying for other, simpler reasons.

"Magnets have been fascinating people for thousands of years," Zutic says. "Some of this fascination was not always related to how you can make a better compass or a better computer hard drive. It was just peculiar that you have materials that attract one another, and you wanted to know why."

Zutic's research on magnetism is funded by the Department of Energy, Office of Naval Research, Air Force Office of Scientific Research and the National Science Foundation.

The University at Buffalo is a premier research-intensive public university, a flagship institution in the State University of New York system and its largest and most comprehensive campus. UB's more than 28,000 students pursue their academic interests through more than 300 undergraduate, graduate and professional degree programs. Founded in 1846, the University at Buffalo is a member of the Association of American Universities.

Charlotte Hsu | EurekAlert!
Further information:
http://www.buffalo.edu

More articles from Physics and Astronomy:

nachricht Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>