Reddit mentions of EFH Series Ferrofluid (60 ml) 2 Oz

That business exists! It's called Amazon!

https://www.amazon.com/dp/B008H40M72/ref=cm_sw_r_cp_api_i_qyh2BbA37H0ZN

It’s not stupid expensive. About $20 for 2oz, and you wouldn’t need much for a more modestly sized device.

> Is that also true for unmagnetized neodymium?

Yup! For almost all magnetic materials the permeability will be the same whether or not they are "set". One exception is in extremely high quality transformer steel- this stuff is specially rolled so its anisotropic. It's flattened into strips, which squishes its crystal structure into very long, thin needles. The atoms inside the needles can flip around easily, but they can only line up in the direction of the needles. They swap back and forth very, very easily, but they can't do the same for side-to-side fields. Once they're set they have great permeability in one direction and mediocre permeability in other directions.

Neodymium magnets have essentially the same structure- very long needle-like magnetic sections, but they're extremely resistant to being turned around. Even the individual neodymium atoms (which are the field-carrying component) are essentially locked in place by their chemical bonds. Iron atoms on the other hand can rotate almost freely; that property is the same one that makes iron (and metals in general) ductile, since the atoms can move with respect to each other.

One of the most important parts of making neodymium magnets is actually an annealing phase, where the magnet is heated for a very long time to line up the magnetic sections. This also has to be done in a low-oxygen atmosphere, and is one of the big reasons neodymium magnets are expensive. Without annealing the magnetic fields cancel each other out to a large degree, so an un-set magnet can have an even lower permeability than a set magnet- but a set neodymium magnet will have almost zero permeability in directions other than the magnetic field.

> I bought some neodymium magnets several years ago to play with and they are amazingly strong.

I love them! Pick up some ferrofluid too, but be careful as it will stain anything practically permanently. The color comes from nanoscale (<10 nm) iron particles that will just nestle into cracks on anything less porous than glass, which is essentially everything. Ferrofluid got me the brainwave of understanding why iron particles line up the way they do.

Another cool thing is that we're finding requirements for even stronger magnets! In very high-end motors, it's becoming more common to use "funnels" of electrical steel to concentrate the power of magnets even farther. Pairs of magnets are tilted to form a triangle with the surface of the rotor- the flux is forced down into a smaller area, making it even stronger! That gives motors more torque for their size.

https://en.wikipedia.org/wiki/Ferrofluid

https://www.amazon.com/CMS-Magnetics-Ferrofluid-Magnets-Dropper/dp/B008H40M72

cheaper ferrofluid: https://www.amazon.com/CMS-Magnetics-Ferrofluid-Magnets-Dropper/dp/B008H40M72