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Novel way to make permanent magnets causes less environmental damage

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A new way to make permanent magnets, which typically have a negative environmental impact when produced, has been developed that has a much lower impact.

Most permanent magnets are made from alloys of rare earth metals, the mining and processing of which produces toxic by-products that can lead to ecological challenges around rare-earth mines and refineries.

Demand for permanent magnets is also increasing as they are a common component in renewable energy, consumer electronics and electric vehicles.

University of Leeds scientists believe they have made a breakthrough in a new advanced material, which may eventually replace rare-earth-based permanent magnets.

The researchers have developed a hybrid film from a thin layer of cobalt, which is naturally magnetic, covered with molecules of Buckminsterfullerene, a form of carbon.

The presence of the carbon dramatically boosted cobalt’s magnetic energy product, a measure of the strength of a magnet, by five times at low temperatures.

The research team observed the increase in magnetic strength at -195°C , but they hope by chemically manipulating the carbon molecules, they will be able to get the same effect at room temperature.

Co-principal investigator Dr Tim Moorsom said: “This is the first indication I have seen that a rare-earth-free magnet could compare to something like samarium cobalt, a rare-earth-based permanent magnet.

“While we have only seen this effect at low temperatures thus far, I am hopeful that a hybrid magnetic material similar to this will one day replace rare earth permanent magnets, helping to mitigate the environmental damage they cause.”

Although carbon is not magnetic, the way the molecules bond to the cobalt surface causes a magnetic pinning effect, which prevents the magnetism in the cobalt from changing direction, even in strong opposing fields. This surface interaction is the key to the unusually high magnetic energy of the hybrid material.

While it may be a long time before hybrid magnets are ready to be used in wind turbines or electric cars, there are other applications which are closer at hand.

Co-principal investigator Dr Oscar Cespedes, said: “Although room temperature applications in bulk permanent magnetism may be a long way off, the use of molecular coupling to tune the magnetic properties of thin films, for example in magnetic memories, is a tantalising prospect that is within easy reach.”

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