For the first time, a miniature magnet competes in strength with magnetic monsters

A magnet small enough to fit in the palm of your hand can for the first time match the strength of some of the most powerful magnets in the world.

Strong magnets play many roles in science and technology, and are used in everything from magnetic resonance imaging and particle accelerators to nuclear fusion efforts. The most powerful of these are made of superconductors, materials that conduct electricity with near-perfect efficiency.

But superconducting magnets that create strong magnetic fields are often bulky: smaller ones are usually the same size as the magnets Star Wars robot R2D2, while the largest are comparable to a two-story building, he says Alexander Barnes at ETH Zurich in Switzerland.

He and his colleagues have now built a superconducting magnet that is competitive with these large magnets in strength but only measures 3.1 millimeters in diameter. They made it by twisting a thin ribbon of a ceramic material called REBCO, which superconducts when cooled to extremely low temperatures. These coils create magnetic fields when an electric current passes through them.

The team bought REBCO tape from a commercial company and then set out to find the best magnet design, which involved making and testing more than 150 of them, Barnes says. “Our strategy has been to develop and adopt a ‘fail often, fail fast’ approach.

They eventually settled on a design that included either two or four pancake-shaped REBCO coils that could produce magnetic fields of 38 Tesla and 42 Tesla. By comparison, a refrigerator magnet typically has a magnetic field strength below 0.01 Tesla. The two magnets, which currently produce the strongest stable magnetic fields in the world, reach around 45 Tesla, weigh many tons and require up to 30 megawatts of power. Barnes and his team’s magnet is smaller than your hand and requires less than 1 watt of power.

Barnes says their ultimate goal is to use this magnet for nuclear magnetic resonance (NMR), an experimental technique that uses magnetic fields to reveal the structure of molecules such as drugs and catalysts for industrial processes. In his view, this powerful technique is hampered by how large and expensive the magnets are, but the researchers hope to make it available to more chemists. The team has already begun testing the magnet in an NMR setup, Barnes says.

“Producing magnetic fields above 40 Tesla has traditionally required very large and expensive devices, so achieving a similar field strength in such a compact device using superconducting tapes is significant,” he says. Mark Ainslie at King’s College London. “It suggests that extremely high-field magnets could become more accessible to a wider range of laboratories in the near future.”

Before the magnet reaches widespread use, however, questions remain — such as how a uniform magnetic field can be created and how the electromagnetic behavior of these coils can be controlled and controlled, he says.

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