BUFFALO, N.Y. -- At the smallest scales, magnetism may not work quite the way scientists expected, according to a recent paper in Physical Review Letters by Rafał Oszwałdowski and Igor utić 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 (http://www.buffalo.edu/news/pdf/June11/Paper1.pdf), 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 abl
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