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

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

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

He and his colleagues have now built a superconducting magnet that is competitive with those large magnets in strength, but measures only 3.1 millimetres in diameter. They made it by coiling a thin tape of a ceramic material called REBCO, which superconducts when cooled to extremely low temperatures. These coils produce magnetic fields when electric currents are passed through them.

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

They ultimately settled on a design that involves either two or four pancake-shaped coils of REBCO that could produce magnetic fields with strengths of 38 tesla and 42 tesla, respectively. For comparison, a fridge magnet typically has a magnetic field strength under 0.01 tesla. The two magnets that currently produce the world’s strongest steady magnetic fields reach around 45 tesla, weigh many tonnes 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.

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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 stymied by how big and expensive magnets are, but the researchers hope to make it accessible for more chemists. The team has already begun testing the magnet in an NMR setup, says Barnes.

“Producing magnetic fields above 40 tesla traditionally requires very large and expensive facilities, so achieving similar field strengths in such a compact device using superconducting tapes is significant,” says 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.”

But questions remain before the magnet can achieve widespread use – for instance, how uniform the magnetic field can be made and how the electromagnetic behaviour of these coils can be managed and controlled, he says.

Jellyfish-shaped robots made of magnetic ferrofluid can be controlled by light through an underwater obstacle course. Swarms of these soft robots could be useful for delivering chemicals throughout a liquid mixture or moving fluids through a lab-on-a-chip.

Ferrofluid droplets are made of magnetic nanoparticles suspended in oil, and they can move across flat surfaces or change shape when coaxed in different directions by magnets. By immersing these droplets in water and exposing them to light, at the Max Planck Institute for Intelligent Systems in Germany and his colleagues have now made them defy gravity.

When ferrofluids absorb light – they are particularly good at that because they are dark – they heat up and any tiny bubbles within them expand. This makes the droplets lighter and more buoyant when they are under water, so they can float upwards, says Sun.

He and his colleagues created soft robots with a droplet of ferrofluid encased in a shell of hydrogel shaped like a jellyfish. Then they put them to the test. The researchers devised an obstacle course at the bottom of a tank of water, which included various platforms at different heights. They directed the robots through it, making them move up and over the platforms.

In one experiment, they arranged three of the jellyfish robots in a line at the bottom of a water tank and used a laser to heat them up. The robots moved upwards in succession, one after another. Sunlight focused through a magnifying glass had a similar effect, making the jellies float vertically.

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at Arizona State University says controlling a whole swarm of droplets simultaneously could be useful in a future where they deliver drugs or perform other functions inside the human body. He says encasing them in hydrogel allows for complex motion, because light can be used to direct the ferrofluid droplet as well as to make the hydrogel itself move.

However, Marvi says many details, including the safety of ingesting ferrofluids, must be worked out before medical uses are possible. Sun and his colleagues hope to answer some of these open questions. For instance, they want to figure out how to use an optical fibre, which could enter the body, instead of lasers or sunlight to direct the robots.

A new kind of magnetism has been measured for the first time. Altermagnets, which contain a blend of properties from different classes of existing magnets, could be used to make high capacity and fast memory devices or new kinds of magnetic computers.

Until the 20th century, there was thought to be only one kind of permanent magnet, a ferromagnet, the effects of which can be seen in objects with relatively strong external magnetic fields like fridge magnets or compass needles.

These fields are caused by the magnetic spins of the magnets’ electrons lining up in one direction.

But, in the 1930s, French physicist Louis Néel discovered another kind of magnetism, called antiferromagnetism, where the electrons’ spins are alternately up and down. Although antiferromagnets lack the external fields of ferromagnets, they do show interesting internal magnetic properties because of the alternating spins.

Then in 2019, , which couldn’t be explained by the conventional theory of alternating spins. The current was moving without any external magnetic field.

It seemed, when looking at a crystal in terms of sheets of spins, that Altermagnets would look like antiferromagnets, but the sheets of spins would look the same when rotated from any angle. This would explain the Hall effect, but no one had seen the electronic signature of this structure itself, so scientists were unsure whether it was definitely a new kind of magnetism.

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Now,  at the Paul Scherrer Institute in Villigen, Switzerland, and his colleagues have confirmed the existence of an altermagnet by measuring the electron structure in a crystal, manganese telluride, that was previously thought to be antiferromagnetic.

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To do this, they gauged how light bounced off manganese telluride to find the energies and speeds of the electrons inside the crystal. After mapping out these electrons, they were found to almost exactly match the predictions given by simulations for an altermagnetic material.

The electrons seemed to be split into two groups, which allows them more movement inside the crystal and is the source of the unusual altermagnetic properties. “This gave direct evidence that we can talk about altermagnets and that they behave exactly as predicted by theory,” says Krempaský.

This electron grouping seems to come from the atoms of tellurium, which is non-magnetic, in the crystal structure, which separate the magnetic charges of the manganese into their own planes and allow the unusual rotational symmetry.

“It’s really nice verification that these materials do exist,” says at the University of York, UK. As well as the electrons in altermagnets being freer to move than those in antiferromagnets, this new type of magnet also doesn’t have external magnetic fields like in ferromagnets, says Evans, so you can use them to make magnetic devices that don’t interfere with each other.

The property could boost the storage on computer hard drives, because commercial devices contain ferromagnetic material that is so tightly packed that the material’s external magnetic fields start to see interference – altermagnets could be packed more densely.

The magnets could even lead to spintronic computers that use magnetic spin instead of current to perform their measurements and calculations, says at the University of Leeds, UK, combining memory and computer chips into one device. “It maybe gives more hope to the idea that we could make spintronic devices become a reality,” says Barker.