How were rare earth magnets discovered?

Was this basically serendipity - someone messing around in the lab - or was there some scientific prediction involved (quantum mechanics, electron orbitals etc)? There doesn’t seem to be a lot of information about this on the Internet…?

It was directed research under the auspices of the Air Force Materials Laboratory. Humans had known about naturally magnetic materials for centuries, but not a a way to produce strong, permanent magnets.

I do not understand any of the chemistry or other science in that link.

It appears that one of the discovers had been researching that particular material for quite a while in the hope that it could generate stronger magnetism. Can’t say whether he was using quantum theory, but it sounds more like observation-guided investigation.

Interesting that this paper remarks: “While SmCo5-based magnets were well on their way toward commercial production when this research program began…”

So there was obviously some previous work?

Interesting article, thanks. Seems that there are a number of people are mentioned as pioneers in the field, notably Dr Strnat. What I wonder though, is what originally led them to look at rare earth elements as possible magnet constituents in the first place?

I guess it could have just been general research into properties of rare earth once they became fairly available in pure form?

Of course the question I am sort of pondering: is there any deep theoretical basis for predicting this kind of property? The same could be asked for superconductivity, of course!

Probably the observation that the lanthanides were strongly ferromagnetic (i.e magnetic in the same way iron is magnetic), but only when cooled. This suggests that a way to stabilize the ferromagnetism to a higher temperature by alloying the metal would be a reasonable approach.

The lanthanides have lots of unpaired electrons in the electron shell structure (lanthinides are filling the f subshell which can hold up to 14 electrons, so a maximum of 7 unpaired electrons). Paired electrons always have opposing spin (that’s a quantum mechanics effect) so the magnetic moment cancels out. Unpaired electrons can align spin, and the more you have the stronger the magnetic moment.

Combine lanthides with an alloying metal that stabilises the ferromagnetism above room temperature, and you can preserve the high magnetic moment of those unpaired electrons. Of course, the specifics of the alloy takes some experimentation. Theory can only take you so far …

A similar pondering: I wonder how much of the “combination space” of the periodic table remains unexplored? Maybe there are materials with marvelous properties that we just haven’t stumbled across yet?
Chemistry is great fun… if I were younger I might think of switching career tracks & going back to university to study it more seriously!

It’s a huge space, even if we’re just talking about materials (as opposed to, say, pharmacologically active small organic molecules.) It’s tricky because small changes in composition can yield large changes in properties. And, properties are path-dependent; the same composition can have different properties just from something like different heat treatments.

More reading here:

The research path for superconductivity is straightforward enough. Most conductors conduct better the colder they get, in a roughly linear way: This has been known all the way since Ohm. And if you take the resistivity as a function of temperature, for “normal” temperatures, and extrapolate it down, you would expect that the resistivity goes down to zero at around absolute zero temperature. So it makes sense to test the resistivity of materials at close to absolute zero.

When you do that, you find something interesting: Generally speaking, that linear relationship holds, until you get down to around liquid helium temperatures (a few degrees above absolute zero), at which point the resistivity abruptly jumps down to zero, instead of continuing on its slope. And this happens, at some temperature or another, to nearly every material, even ones that aren’t very good conductors at room temperature. So then it’s straightforward to ask what the highest temperature is that you can get, and from what material.

Now, actually finding those materials, that takes lots of theory and lots of experimentation. But knowing to look for them, that part is straightforward.

That reference states that " In Japan in 1938, it was learned that permanent magnets could be created from powdered oxides, such as iron oxide."

It was already known that the stone called “magnetite” was “iron oxide” (Fe3O4), and “sintering” was not a new process, so either that means someone described a process of creating magnetic stones, or it means that some one started using a process of creating magnetic stones.

I’m fairly sure that it doesn’t mean anyone understood a process of creating magnets, because the post-war textbooks in my library had the physical behavior wrong, and that only changed when new developments in grain analysis merged with new developments in physics.