What is the smallest permanent magnet? Is it possible to make a permanent magnet 50 microns in diameter?
Fifty microns--the approximate diameter of a human hair--is ginormous from the standpoint of solid state physics, and smaller magnets have been observed in nature or manufactured in labs. Some examples:
State of the art hard drives have magnetic bits which are ~10nm in size
Ferrofluid is composed of magnetic nanoparticles (coated with a surfactant) which are ~10nm in diameter
Magnetotactic bacteria can orient themselves to the earth's magnetic field because they contain magnetic nanoparticles which are 50-100nm in diameter
I have had custom magnets built for me using regular sinter+pole+machining technologies, that had dimensions on the order of 0.1x0.4x3 mm. I have made my own permanent magnets using AlN that had dimensions 0.002x0.05x0.3 mms. So yes.
Some SAC balls used in ball grid array soldering already come magnetized for special use cases and they have dimensions all the way between 8 to 200 microns.
The smallest magnet is a single atom of iron.
