|
Theresearcher have found a new property which can be quite beneficial infield of computing. They found that the new "superatoms" � clusters ofatoms that share electrons and can mimic the behaviour of otherelements � have been devised with magnetic properties for the firsttime. The breakthrough provides a way to design novel nano-scalebuilding blocks with controllable magnetic properties that could beused to make faster computer processors and denser memory storage.Superatomswere discovered in the 1980s when Walter Knight and colleagues foundthat groups of sodium atoms can share electrons amongst themselves. Theelectrons form a collective "supershell" that coats the cluster. Thesupershell behaves much the same way as the outer electrons on regularelements, masking the superatom's true chemical identity. Chemists havesince discovered a host of other superatoms � mainly aluminium clustersthat react like other elements, such as the noble gases helium or argon.Suchmimicry could help create more efficient fuels, since aluminium powderreleases huge amounts of energy when it burns, but reacts with otherelements too quickly to be useful as a solid fuel additive. Inaluminium clusters that behave chemically like noble gases, however,the metal could hide out until it became activated by the burning ofthe fuel. Until now, however, clusters that copy the magneticproperties of other elements have proved more difficult to design.Magnetismis caused by the spin of an atom's electrons, which are arranged inshells, or orbitals, around the atom's nucleus. Their net spindetermines the strength of the atom's magnetic "moment", and becausethey tend to occur in pairs that cancel each other out, it is theatom's unpaired electrons that contribute to its magnetic moment.Unpairedelectrons, however, will make an atom, or a superatom, more likely toreact with others in an attempt to fill its orbitals and become stable.As a result, stability and magnetism have long been thought to bemutually exclusive.The researchers worked out that encapsulating anatom of vanadium in a cage of eight caesium atoms would create a stablesupershell of electrons around the entire cluster. This would preventthe vanadium atom's unpaired electrons from reacting with other atoms,maintaining its magnetism. The arrangement would yield a magneticmoment of five Bohr magnetons, which is the same as an atom ofmanganese.There's no limit to the number of new magneticclusters waiting to be discovered, and his team has since designedmagnetic superatoms made of vanadium encapsulated in sodium, andmanganese in gold.In each case, the cluster has both a magneticmoment and a filled supershell, making it stable.It could be possiblethat stable magnetic clusters could one day be used in new "spintronic"devices, which compute or store information using magnetic momentsrather than simply electrical charge. Encoding data in this way meansthe devices can be far smaller than those used to make conventionalelectronic components, potentially providing an overall boost incomputing power.
|
