When you squeeze atoms, you don't get atom juice. You get magnets.
According to a new theory by Rice University scientists, imperfections in certain two-dimensional materials create the conditions by which nanoscale magnetic fields arise.
Calculations by the lab of Rice theoretical physicist Boris Yakobson show these imperfections, called grain boundaries, in two-dimensional semiconducting materials known as dichalcogenides can be magnetic. This may lead to new strategies for the growing field of spintronics, which takes advantage of the intrinsic spin of electrons and their associated magnetic fields for electronic and computing devices.
The discovery by Yakobson, lead author Zhuhua Zhang and their colleagues was reported online this week in the American Chemical Society journal ACS Nano.
Dichalcogenides are hybrids that combine transition metal and chalcogen atoms, which include sulfur, selenium and tellurium. The Yakobson group focused on semiconducting molybdenum disulfide (MDS) that, like atom-thick graphene, can be grown via chemical vapor deposition (CVD), among other methods. In a CVD furnace, atoms arrange themselves around a catalyst seed into familiar hexagonal patterns; however, in the case of MDS, sulfur atoms in the lattice alternately float above and below the layer of molybdenum.
When two growing blooms meet, they're highly unlikely to line up, so the atoms find a way to connect along the border, or grain boundary. Instead of regular hexagons, the atoms are forced to find equilibrium by forming adjoining rings known as dislocations, with either five-plus-seven nodes or four-plus-eight nodes.
In graphene, which is generally considered the strongest material on Earth, these dislocations are weak points. But in MDS or other dichalcogenides, they have unique properties.
"It doesn't matter how you grow them," Yakobson said. "These misoriented areas eventually collide, and that's wh
|Contact: David Ruth|