Better magnetic refrigeration.

In some materials, a magnetic field can cause cooling.

Scientists have known about this phenomenon, the magnetocaloric effect, since the turn of the century, when the technique was first used to cool liquid oxygen.

In essence, the effect works like this: Exposing a substance to a magnetic field causes its atoms to point in the same direction. When that magnetic field is taken away, the atoms rotate randomly. This change creates a cooling effect.

Near absolute zero, this effect works very well. Above 15 kelvins, however, existing materials don't cool effectively. The problem, says Robert D. Shull, a researcher at the National Institute of Standards and Technology in Gaithersburg, Md., stems from inherent limitations in the cooled compounds.

"To increase the operating temperature of a magnetic refrigerator," he says, "we need new materials."

Shyll's group now reports making a new composite that shows a magnetocaloric effect three to four times larger than the effect exhibited by current materials. Made of gadolinium, gallium, iron, and oxygen, the new substance produces cooling at less frigid temperatures, and it requires a less intense magnetic field, Shull says.

Household magnetic air conditioners and fridges remain a long way off. At present, magnetic cooling requires temperatures near absolute zero, making this technique impractical for home use. but Shull believes that, at least in theory, magnetically cooled ice cream "is possible."