>As far as I know, that’s possible with permanent magnets (and it would be weird, but not impossible, if the group instead synthesized a novel ferromagnet and didn’t notice)
As far as I know a stable arrangement of permanent magnets levitating is impossible without a baring surface to keep them aligned. (i.e. free floating levitation is not possible without active control)
* ferromagnetic - attracted to one pole of a magnet but not the other (in a given orientation), this is what everybody thinks of when they think of "magnets"
* paramagnetic - attracted to both poles, i.e. stuff that sticks to magnets
* diamagnetic - repelled by both poles, except in superconductors, this effect is very weak compared to the forces experienced involving ferro-ferro or fero-paramagnetic materials.
There isn't another category, everything fits in to one of those buckets.
Saying
>Just so everyone is on the same page, static passive diamagnetic levitation is possible with materials like pyrolytic graphite.
is a bit deceptive, as what people know as "magnetic" materials are ferromagnetic.
That's not quite true. There is a Halbach array with a bunch of compensation coils that will nicely center as long as it is moving, no active control or bearing required.
stationary. Hence the 'as long as it is moving' bit above. Because the motion allows for the coils to generate enough of a current to drive the compensation. So you need a support system to bring the assembly up to a certain minimum speed above which it will stably levitate.
I wonder how long you could get one of those to spin in a vacuum.
Halbach arrays with compensating coils have been proposed for some interesting applications, such as low loss flywheels for electrical storage. I don't know if that ever got commercialized but I do recall that some prototypes were made by a US company. I can't find a reference to it though.
As far as I know a stable arrangement of permanent magnets levitating is impossible without a baring surface to keep them aligned. (i.e. free floating levitation is not possible without active control)