Commercial prospects for the new superconductor magnesium diboride get a boost this week. Three groups have fashioned the new material into films and wires capable of carrying high currents, helping to allay fears that it might not be suited to practical applications.

A superconductor carries an electrical current without resistance, and might therefore dramatically reduce losses in power transmission. In normal conductors such as metal wires, resistance squanders energy as heat.

Most superconductors work only at very low temperatures. When a Japanese team discovered the surprisingly simple new superconductor magnesium diboride last January, physicists were tantalized by its cheapness and by the relatively high temperatures at which it superconducts: – 234 ^oC (39 K).

But there is one key drawback to magnesium diboride. Magnetic fields disrupt superconductivity -- in magnesium diboride especially so. Because many potential superconductor applications involve exposure to magnetic fields, this is a real drawback.

A magnetic field can render a material non-superconducting, and can reduce the maximum electrical current it can carry. The larger this critical current, the more power the material can carry.

Chang-Beom Eom of the University of Wisconsin at Madison and co-workers inadvertently added a little oxygen to some of their samples of magnesium diboride, and found that it made them more magnet-proof1. Thin films of the material containing more oxygen remained superconducting in stronger magnetic fields. They also supported larger critical currents.

David Caplin of Imperial College in London, UK, and collaborators increase the critical current by blasting the magnesium diboride with an ion beam, a stream of positively charged hydrogen atoms2. Like cannon-balls hitting a castle wall, these ions disrupt the regular atomic structure of the crystals. A magnetic field gets 'snagged' on the resulting defects, reducing its influence on the material's superconductivity.

Sungho Jin and co-workers at Lucent Technologies in New Jersey have focused instead on how to make magnesium diboride into superconducting wires3. Because the material is hard and brittle, it cannot be drawn into wires like a ductile metal.

Often, brittle superconductors are encased, in powdered form, inside metal tubes flattened into ribbons. For magnesium diboride, this approach is complicated by the fact that magnesium reacts with several common metals, such as copper or nickel.

Jin's group finds that iron-clad tubes and ribbons do the trick. They have critical currents similar to a lump of the bulk material, even if a little of the iron gets mixed into the superconductor.

Making wires of magnesium diboride and giving it greater resilience to magnetic fields could see the promising superconductor put to practical use.