# How according QM do permanent magnets rotate?

When two magnets are placed close to each other they turn and orient parallel. I suppose this is due mostly to spin of the unpaired electrons. But in QM a spin just orients up or down. 1. How are these two pictures compatible? If the spin is closer to up projection the magnet shoud first turn up say 25 degrees and then turn 180 if it flips to down) 2. Where from takes the smaller (unfixed) magnet energy to rotate? (I cannot see how energy is taken from the magnets as they are permanent and stay so for many decades)

• The sentence "but in QM spins just orient up or down" is plain wrong. When measuring the projection of spin $1/2$ along any axis, you only get two possible values. But you can choose the axis of measurement as you wish (which just corresponds to a rotation of the basis in which you represent the spin). – Sebastian Riese Oct 28 '19 at 10:03
• orient mean ecxactly this. I can not choose another axis as there are just the two magnets. – Mercury Oct 28 '19 at 11:54
• In fact I have chosen the axis by puttting the fixed magnet in the fixed direction. – Mercury Oct 28 '19 at 12:19