The correlation of electron spins in an object.
An object with randomly aligned electrons will have no net magnetic field.
Once the electron spins line up, this induces a magnetic field gradient.
In some materials - permanent magnets - the changes in spin induced by a strong internal field does not decay.

Both thermal effects and external fields can demagnetise magnets - due to overcoming the potential energy stored in the magnet, and randomising the spins.
(speedevil, Fri 14 Oct 2011, 18:04, 1 reply)

Saying magic would have been quicker.

( mark morrisons prison shoes I love Willie, Fri 14 Oct 2011, 19:06, closed)

And made more sense.

( His Popiness the Hole Invaded Poland on, Sun 16 Oct 2011, 21:07, closed)

but
be no use at all if you wanted to do anything clever with magnetism.
(haberman is singing in the changes, Mon 17 Oct 2011, 22:40, closed)