Physicists Find Seemingly Impossible Magnets With Just One Pole

Sometimes physics comes with loopholes.

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Using a diamond needle tipped with a single electron, physicists have found seemingly impossible one-sided magnets swirling along the surface of hematite.

The rules of physics (the ones we know of, anyway) say that magnets with just one pole should be impossible. But when tiny particles start doing strange things, they can bend the rules. That’s how physicists recently found magnetic monopoles (bits of magnetic matter with just one pole, instead of the usual two) on the surface of hematite. Eventually, those monopoles may help power faster, more energy-efficient computer memory.

University of Oxford physicist Hariom Jani and his colleagues published their findings in the journal Nature Materials.

Hematite is a mineral made of iron oxide, which is the same chemical compound that rust is made of.


North Pole? You Mean the Only Pole

Jani and his colleagues recently found magnets that seemed to have only a single magnetic pole, spawning amid the microscopic swirls on the surface of hematite: a mineral made of iron oxide, the same molecule that makes up rust. It turns out that thanks to the microscopic swirling texture of the hematite’s surface, groups of particles — through the power of their combined rotation — can spawn tiny magnetic fields with a single pole.

We’re all used to magnets having two poles: north and south. That’s true of everything from the magnet that holds your grocery list onto your fridge to the magnetic field of an entire galaxy. If you cut a normal two-pole magnet in half, you’ll end up with two halves that have two poles each. It’s just how magnets work. But some theories, like string theory and the grand unified theory, predict the possibility of monopoles: weird, lopsided magnets with just one pole, either north or south. Physicists have never actually seen one in the wild (or made one in the lab), though, so these so-called monopoles are still purely hypothetical. Like everything in physics, though, there’s a “but…” here.

Sometimes, when groups of particles interact, their combined properties add up to really weird things. Physicists call these emergent properties. And that’s what happens on the surface of hematite, according to Jani and his colleagues’ recent study.

The researchers used an imaging technique called diamond quantum magnetometry to map the tiny magnetic fields on the surface of a piece of hematite. Diamond quantum magnetometry involves using the angular momentum (the force of its rotation, to put it in extremely simplified terms) of an electron, perched at the very tip of a diamond needle, to measure very small magnetic fields without affecting how the fields behave.

On the surface of the hematite, groups of particles join forces (literally, because it’s a product of their combined angular momentum) to create the same effect as a single particle with just one magnetic pole. That’s what physicists call a “quasi-particle,” because it behaves like a single particle, but it’s really the combined effect of lots of particles behaving in a particular way.

All this matters because computer memory is based on magnets, or specifically on magnetic spin. And if we can isolate monopoles — even quasi-particle ones instead of “real” monopole particles — then that gives engineers more control over magnetic spin. It’s even possible that they could “sort and store data based on the north or south direction of their poles — analogous to the ones and zeros in conventional magnetic storage devices,” as Berkeley National Laboratory put it in 2019.

And that, Jani and his colleagues suggest, could lead to more energy-efficient computer memory.

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