What are the three magnetic metals

For the first time magnet made out of copper

Iron, cobalt, nickel - only these three metals are magnetic in their pure form and at room temperature. This property is called ferromagnetic. All rare earth alloys used industrially for permanent magnets contain these three metals. That could change in the future. An international team of researchers has succeeded in transforming non-magnetic metals such as copper and manganese into magnets. As they report in the journal “Nature”, this method could be used to develop magnets from non-toxic and, above all, cheaper substances.

Magnets made of copper and manganese

“By adding organic molecules, we checked whether we could create a magnetic order in non-magnetic metals,” says Oscar Cespedes from the University of Leeds. Together with his colleagues, he succeeded in this magnetic conversion with spherical molecules made up of 60 carbon atoms, the so-called buckyballs or fullerenes. They steamed just 10 to 20 millionths of a millimeter - or nanometer - thin buckyball layers on even thinner layers of copper or manganese.

These sandwich structures showed surprising behavior at the interfaces between metal and carbon. For example, individual electrons were pulled out of their original positions in the metal layer at room temperature. Thanks to this movement, the electrons could now permanently carry a magnetic spin. The sum of these spins laid the basis for the measurable magnetism of the various sandwich structures. However, the metal layers were not allowed to be thicker than 2.5 nanometers, as the magnetism would then disappear again.

With this experiment, Cespedes and colleagues succeeded for the first time in meeting the so-called Stoner criterion for ferromagnets at room temperature without the elements iron, cobalt and nickel. This criterion, named after the British physicist Edmund Clifton Stoner (1899-1968), describes the behavior of the electrons that is necessary for ferromagnetism.

However, the strength of these copper and manganese magnets was very small and could only be measured with highly sensitive magnetometers. "At the moment, none of these magnets would stick to a refrigerator," says Cespedes. The researchers hope, however, that stronger magnets could be developed with other material combinations. In the longer term, this might reduce the dependence of European industry on imports of rare earths.

Until then, Cespedes sees his magnets as contrast media in medicine or as tools for building qubits in quantum computers. “Our trick definitely expands the number of magnetic substances from cheap, readily available and environmentally friendly components,” says Cespedes.