Why do aligned electron spins create a magnetic field?

[Rockazella]

My physics teacher gave the class a brief explanation of a permanent magnet. If I understood him correctly he basically said the special condition with a permanent magnet is that all the electrons are circling uniformly (in same direction). The poles of the magnet are based on the direction the electrons are spinning (right hand rule).

My question is why would those uniform circling electrons cause a magnetic field?

 

[Alexander]

They actually don't circle all uniformly, but never mind the difference.

Basicly each orbiting electron can be considered as a current loop (it is quantum loop, but that is unimportant here). If loops are randomly oriented, then macroscopic magnetic field (average over many atoms) is zero, but if there is predominant orientation then average field is not zero any more, and we call an object with such orientations "a magnet".