Scientists Find Superconductor that is Virtually Immune to Magnetism

Tag : CUPRIC OXIDE


DailyTech has been extensively covering the breakthroughs in superconductors over the last couple years. The class of materials is verypromising in that if someday it could replace conductors, it wouldmean that electricity could travel at virtually no losses toanywhere in the world. This would result in vast energy savingsand allow for dramatically faster computers, free of the burden ofresistance-produced waste heat.

Standing in the way of the advances are three critical weaknessesof superconductors. The first and most well known is theirtemperature dependence. Superconductors must be beneath a criticaltemperature to superconduct. Typically this critical temperatureis extremely low, well beneath the means of even standard liquidnitrogen cooling. The critical temperature is somewhat pressuredependent, so extremely high pressure superconductors can superconduct at higher temperatures .

Recent non-high pressure superconductors have upped the standard T c to around 138 K (-200 °F). Recently Superconductor.org found a cupric-lead-tin-oxide superconductor , (Sn 1.0 Pb 0.5 In 0.5 )Ba 4 Tm 5 Cu 7 O 20 , with a T c of 185.6 K.

The other two lesser known limitations of superconductors are highcurrent and magnetism. At high current, superconductors can ceaseto function properly. Magnetic fields are particularly deadly tosuperconductors. Typically, even a small magnet field will reverta superconductor back to a normal conductor.

A new breakthrough from scientists has found a unique class ofsuperconductors which seem to be amazingly almost completely immune to magnetism . This is a significant breakthrough as it could remove one of thelargest obstacles to commercializing superconducting.

The new material was first discovered by Japanese researchers earlythis year that had been looking into iron-superconductors, anatypical choice for superconductor metals, and added a bit ofarsenic to the mix. The new iron oxyarsenide -- which alsofeatured oxygen, as the name implies -- superconductor. The newmaterial, which also contained the rare earth metal lanthanum,could superconduct at 26 K (-413 °F).

The researchers were somewhat surprised to find a fully workingsuperconductor with iron as iron typically creates a magnetic fieldwhen conducting. Somehow the superconductor was surviving amagnetic field, an unexpected first.

Now researchers David Larbalestier, Alex Gurevich and JanJaroszynski, and colleagues in David Mandrus' groupat Oak RidgeNational Laboratory in Tennessee and Frank Hunte, a postdoctoralassociate at the Applied Superconductivity Center (ASC) of theNational High Magnetic Field Laboratory at Florida State Universityhave investigated the phenomena in more depth and synthesized newiron superconductors.

The researchers reported their findings (PDF) in the prestigious journal Nature . Larbalestier, director of the ASC states, "What one would likeis a greater selection of superconductors, operating at highertemperatures, being cheaper, possibly being more capable of beingmade into round wires. Iron and arsenic, both inherently cheapmaterials, are key constituents of this totally new class ofsuperconductors. We're just fascinated. It's superconductivity inplaces you never thought of."

The researchers put the new superconductors to the test, placingthem within Oak Ridge National Laboratory's 45-tesla Hybrid magnet,one of the most powerful research magnets in existence. Researchers expected the magnet to be sufficient to kill thesuperconductor, but to their surprise it tolerated it and washealthily superconducting even at the magnetic field's full power.

On a technical side the research yields an even greater mystery,perhaps indicating that we know less about superconduction than wethink we do. Superconduction on an atomic level has long beenthough to occur through so-called "Cooper pairs", paired electronswith opposite spin, momentum, etc. Magnetism was thought to breakthese pairs. Either iron has some sort of unique way of keepingthe pairs bonded, or the current model is incomplete or flawed.

A third possibility is that Cooper pairs are only one method ofsuperconduction, and that the new material utilizes a newmechanism. Says Hunte, "So far based on both theoreticalcalculations and what we're seeing from the experiments, it seemslikely that this is a completely different mechanism forsuperconductivity."

Possible applications of the new tech include ultra-efficientsuperconducting motors and power transmission lines. They couldalso be used in new superconducting magnets, which would open up anew world of research opportunities in diverse fields of science. Hunte states, "The field is completely open. No one knows wherethis is going to go. If it's found that these materials cansupport high current densities, then they could be tremendouslyuseful."