Miniature magnet rivals magnetic behemoths in strength for the first time

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

Powerful magnets play many roles in science and technology, with uses in everything from MRI imaging and particle accelerators to nuclear fusion efforts. The most powerful of them are made from superconductors, materials that conduct electricity with near-perfect efficiency.

But superconducting magnets that produce powerful magnetic fields are often large: the smallest are generally the same size as the Star Wars R2D2 robot, while the larger ones are comparable to a two-story building, says Alexander Barnes of ETH Zurich in Switzerland.

He and his colleagues have now built a superconducting magnet that rivals these large magnets in strength, but measures only 3.1 millimeters in diameter. They made it by rolling a thin ribbon of a ceramic material called REBCO, which becomes superconductive when cooled to extremely low temperatures. These coils produce magnetic fields when electric currents pass through them.

The team purchased the REBCO strip from a commercial company, then set out to find the best magnet model, which involved manufacturing and testing more than 150 of them, Barnes says. “Our strategy was to develop and adopt a ‘fail often and fail fast’ approach.

They ultimately settled on a design involving two or four pancake-shaped REBCO coils that could produce magnetic fields with strengths of 38 Tesla and 42 Tesla, respectively. For comparison, a refrigerator magnet typically has a magnetic field strength of less than 0.01 Tesla. The two magnets that currently produce the strongest stable magnetic fields in the world reach around 45 Tesla, weigh several 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. He says the powerful technique is hampered by the size and cost of the magnets, but researchers hope to make it accessible to more chemists. The team has already begun testing the magnet in an NMR setup, Barnes says.

“Producing magnetic fields above 40 Tesla traditionally requires very large and expensive facilities. It is therefore important to achieve similar field strengths in such a compact device using superconducting tapes,” explains Mark Ainslie of King’s College London. “This suggests that extremely high-field magnets may become more accessible to a wider range of laboratories in the near future.”

But questions remain before the magnet can be widely used – for example, how to make the magnetic field uniform and how to manage and control the electromagnetic behavior of these coils, he says.