67. Holmium: This Magnet Moment

Holmium: Equally beloved by theoretical physicists and Jedi Knights.

Featured above: Lovely Stockholm! Photo by Edward Stojakovic, CC BY 2.0.

Show Notes

Further show notes coming soon; in the meantime, here’s a fuller explanation of magnetic monopoles from CERN:


Episode Script

As part of a young Jedi’s training, they are tasked with constructing their own lightsaber. It’s not as simple as buying a kit from the Jedi Academy Bookstore, either. The trainee must venture into the Crystal Caves on the ice planet Ilum in search of a kyber crystal worthy of their weapon. It is this crystal that channels the lightsaber’s energy, producing a blade of pure energy so intense that it can instantly cauterize the very wounds it inflicts as it slices through some evildoer’s flesh.

Sadly, this elegant weapon only exists in a galaxy far, far away — at least for now. But any would-be Jedi trying to make a real-life lightsaber might want to start by taking a look at element 67. The most powerful surgical lasers on earth work by focusing light through a crystal that contains holmium. They’re so powerful that they can cut right through flesh — and at the same time, cauterize the very wounds they’re inflicting. The light of these lasers even happens to be a rich emerald-green color, just like the lightsaber wielded by Luke Skywalker in Return of the Jedi.

It might not be very practical when facing down an evil empire, but it is infinitely more useful than a lightsaber would be when trying to remove a kidney stone.1

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re developing an unlikely emotional connection with holmium.

Most of the lanthanides we’ve investigated have involved a cast of recurring characters, a small group of scientists who each had a hand in the discoveries of several rare earth elements. Holmium offers a bit of a palate cleanser, then. Entirely absent from its history are Mosander, de Boisbaudran, and Klaproth, making way for three totally new European men.

In 1878, Jacques-Louis Soret and Marc Delafontaine were inspecting samples of rare earth minerals when they discovered a new and unique set of lines in their spectroscope. They gave this new substance a most intriguing name: “Element X.”2

The following year, Swedish chemist Per Teodor Cleve (klee-veh) independently made the same discovery while investigating minerals from where else? Ytterby. He was prepared to give the substance a more traditional name. The only problem was, by this time, other scientists had already discovered and named yttrium, ytterbium, terbium, and erbium. There just aren’t many other ways to slice up “Ytterby.” So he did the next-best thing and named this element after the nearest big city:3

Lovely Stockholm! A city of nearly one million people, spread across fourteen islands, connected by 57 bridges and 800 kilometers of bike paths. The land has been inhabited since prehistory, but was officially founded in 1252 by Birger Jarl. The city is home to nearly 100 museums, including the Vasa Maritime Museum and one that’s dedicated entirely to beloved Eurovision sensation ABBA. Be sure to visit the Ericsson Globe Arena, the largest hemispherical building in the world!4 And every year on the tenth of December, the Stockholm Concert Hall holds the Prize Award Ceremony for the Nobel Prizes in Literature, Medicine, Physics, and Chemistry.5

The periodic table is full of names taken from various places, also known as “toponyms.” A whole host of regions, countries, and even celestial bodies are represented among the elements. But only eight cities have been given this honor, and Stockholm takes its place alongside cities as cosmopolitan as Paris and as tiny as Strontian. And, obviously, Ytterby.

But what sets holmium apart from all the other elements is that it has the highest magnetic moment. The magnetic moment is simply a measurement that tells you the strength of the magnetic field it can generate. Somewhat confusingly, holmium itself is not naturally ferromagnetic — at least, not at room temperature — but it becomes ferromagnetic when it’s exposed to a magnetic field.6

So even though it doesn’t make a great magnet by itself, holmium can really boost a magnet’s strength. A device that does this is called a “flux concentrator.”7 I’m sorry to say that you cannot hook up a flux concentrator to a DeLorean to travel back in time, but it is a critical component of Magnetic Resonance Imaging machines, and those are nearly as incredible as a time machine.

We learned a little about MRI scanners in episode 64, but they allow an operator to create fully detailed 3D images of a person’s insides. By spending just a few minutes inside a tube, a doctor can get up close and personal with a patient’s internal anatomy. All without making a single incision.8

Since their development in the 1970s, MRI machines have revolutionized medicine — and several other sciences, too. In fact, one of those aforementioned Nobel Prizes was awarded to Paul Lauterbur in 2003 for the work he conducted, which made MRI machines possible.

It’s possible that holmium could enable a magnetic phenomenon even more impressive than that: The magnetic monopole.

As far as anyone’s seen, every magnet is a dipole. That is to say, they have two poles: one north, and one south. If you cut a magnet in half, now both halves each have their own north pole and south pole.

A magnetic monopole would be, well, just what it sounds like: a magnet with only one pole. It would have a magnetic charge, either all north or all south.9 10 11

If that sounds a little confusing, it might help to think of it less like a bar magnet and more like an electron. Electrons also carry a charge — it just happens to be electric rather than magnetic.

Theoretically, magnetic monopoles could exist. In fact, some very important theories operate on the assumption that they do exist, making this one of those minor details with ramifications for all known physics, depending on whether it actually exists or not.

In 2009, a team of scientists was able to manipulate molecules of holmium titanate in such a way that, under very particular conditions, those molecules acted the way a magnetic monopole would act. It was an exciting discovery, but not quite the real thing. Physicist Kimball Milton explained to Discover Magazine, “I might object to [the researchers] saying ‘genuine magnetic monopoles,’ because when you say genuine, that implies that it’s a point particle, and it’s not. It’s an effective excitation that at some level looks like a monopole, but it’s not really fundamentally a monopole.”12 13

You can’t blame Dr. Kimball for raining on this parade. These very fine distinctions are actually important in the realm of theoretical physics — just one way the field differs from horseshoes, hand grenades, and engineering.

Holmium may yet be responsible for another grand magnetic achievement, though. Take hard drives: They store information as bits. One bit of information is either a one or a zero, yes or no, on or off. Each bit is stored by stabilizing a magnetic field in a compound made of millions of atoms. That’s still incredibly small, but shrinking the physical space it takes to store a single bit could help create computers that are not just smaller, but considerably faster, too.

In 2013, researchers at the Karlsruhe Institute of Technology stored a byte in a much smaller space: On a single atom of holmium. By cooling it down close to absolute zero and placing it on a platinum substrate, the team was able to stabilize the atom’s magnetic spin for ten minutes. That might not sound like long, but that’s a billion times longer than previous experiments were able to achieve.14

Granted, the temperature still makes it a little impractical as the storage in your next mobile phone. In fact, all of these applications are a little out of reach for the typical element hunter.

Sadly, holmium just isn’t in very high demand outside of these highly esoteric arenas. The easiest place for you to find it, outside of the minor metals trade, is probably as a colorant for glass or cubic zirconia. So it might not be very practical, but with a little holmium, you can take a look at your element collection through rose-colored glasses.

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel. To see magnetic monopoles explained with a little visual aid, visit episodic table dot com slash H o.

I’m afraid that we did not make it to the next round of judging for the 2020 People’s Choice Podcast Awards. It’s unfortunate, but as the consolatory email said, nearly 500,000 listeners participated in the voting. My sincere thanks to those of you who supported the show. We’ll try again next year.

Next time, we’ll visit well-trod ground with erbium.

Until then, this is T. R. Appleton, reminding you that a flux capacitor can be powered by weapons-grade plutonium, a Mr. Fusion home energy generator, or one well-placed strike of lightning, in a pinch.


  1. Cleveland Clinic, Holmium Laser Lithotripsy.
  2. Chemicool, Holmium Element Facts/Chemistry. Dr. Doug Stewart.
  3. Elementymology And Elements Multidict, Holmium. Peter van der Krogt.
  4. Stockholm Live, Ericsson Globe.
  5. NobelPrize.org, The Nobel Prize Award Ceremonies And Banquets.
  6. Education In Chemistry, Holmium. John Emsley, March 5, 2014.
  7. SEC Electronics, Inc., Flux Concentrators.
  8. Smithsonian Magazine, The “Indomitable” MRI. Julie Wakefield, June 2000.
  9. Science Alert, Our Quest To Find A One-Sided Magnet Just Took An Unexpected Turn. Bec Crew, May 20, 2017.
  10. Phys.org, The Mysterious Missing Magnetic Monopole. T’mir Danger Julius, August 9, 2016.
  11. The Royal Society Of Chemistry, Chemistry In Its Element: Holmium.
  12. Discover, Scientists Hunt For A Seeming Paradox: A Magnet With Only One Pole. Adam Hadhazy, November 12, 2018.
  13. Scientific American, Researchers Claim To Cook Up Isolated Magnetic Poles. John Matson, September 4, 2009.
  14. SciTechDaily, Scientists Stabilize The Magnetic Moment Of Single Holmium Atoms. November 14, 2013.

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