Is it possible to design a large permanent magnet that creates a multi-Tesla field? Is it ever possible to create a LARGE magnet (in meters wide/long) that could potentially create a powerful magnetic field?
 A: Yes, it is already a reality. Permanent magnets from rare earth alloys

https://en.wikipedia.org/wiki/Rare-earth_magnet

can exceed 1.4 tesla while ferrite and ceramic ones only have 0.5-1.0 tesla. Making the material as big as a meter or anything you want is just a matter of accumulating a larger amount of the material (or adding smaller magnets).
At that point, are really approaching the limits of Nature. For example, if we managed to orient all the spins in iron in the same direction, it would produce the magnetic field 2.1 tesla. It's very hard to get much higher than that as long as we only work with permanent static magnets.
A: Using the principle of superposition, it is possible to generate magnetic fields as high as 3-4 T, in small air gaps, using structures built from Nd-Fe-B-based permanent magnets. I was involved in the design and build of structures that could generate highly uniform fields of 2 T+, across an air gap that was 15 cm tall (between the pole faces) and 25 cm wide. required a LOT of Nd-Fe-B to do it, and appropriate pole pieces, but it can be done, no problem. You end up channeling the flux from adjacent magnets into the same air gap, to increase the overall flux density above the magnetic induction or Br of the material itself.
Look up info on Halbach and Stelter arrays for more info.
Gareth Hatch - email: ghatch -at- techmetalsresearch.com
