Is the soft iron core the only method for concentrating magnetic fields?

[Quasaire]

Is the soft iron core the only known way of concentrating magnetism? I know that Halbach arrays create a sort of "monopole" by canceling the field on one side of the magnet but that, in my opinion, is not really concentration but rather asymmetrical field distortion. Afterall, the array doesn't actually transfer the field from one side of the magnet to the other or does it?

And while I'm on the subject does contemporary physics knowledge explain why Halbach arrays work? Isn't it true that Maxwell's equations says monopoles can't exist? It would be like trying to make a sphere on flat paper? Actually I don't understand his equations, as I'm not in that high of math, but so I heard anyway.

 

[Tyger]

Here's a nice link

on Halback arrays, there's plenty more on the web. Surprising how many simple gadgets there are left to invent.

http://www.matchrockets.com/ether/halbach.html

HA are just conventional physics. Imagine a refrigerator magnet made by gluing little horseshoe magnets together so that the dipole field is all on one side, and you get the idea.

There are plenty of materials besides Iron that concentrate magnetism, Iron is cheap and effective. You can also use superconductors to make "permenant" magnets.