Magnetic spin and a magnetic field

[uvicchem]

So I'm starting to read about NMR and I have a very simple question. When we subject a nuclei to a magnetic field, we always draw the spins going with the magnetic field as having lower energy than those going against. If I was to take a huge bar magnet as a field and then took little magnets next to it, opposites will attract. Isn't this the lower energy? So why is it that the lower energy state is the one going with the external field?

Any insight would be greatly appreciated!

 

[granpa]

depends whether its spin up or spin down