Magnetic Surprise: Simple Duo Could Forge Powerful New Magnets

In the quest for new materials, sometimes the simplest combinations hide the most surprising behaviour. Researchers have explored the binary system of cobalt, a known magnetic element, and bismuth, the heaviest stable element. This chemical duo was already known to exhibit superconductivity under certain conditions, but scientists hypothesised it could also be ferromagnetic, a key property of permanent magnets.

Using powerful computer modelling, the team predicted the existence of five new cobalt-bismuth (Co-Bi) compounds. They then tested these predictions in the lab, using high-pressure synthesis to successfully create four new materials. Remarkably, three of these matched the computer-predicted structures, demonstrating the power of this combined theoretical and experimental approach.

Crucially, the modelling predicts that two of the new forms, β-CoBi and β-CoBi2, are ferromagnetic. One of them, β-CoBi, is even predicted to have a greater magnetocrystalline anisotropy—a measure of its ability to resist demagnetisation—than some familiar permanent magnets. This work establishes the simple Co-Bi system as an exciting platform for understanding the foundations of both magnetism and superconductivity.