This is one of the magnetic field effect on radical pairs recombination. Once you put a magnet near the site of a chemical reaction where radical pairs are for

This is one of the magnetic field effect on radical pairs recombination. Once you put a magnet near the site of a chemical reaction where radical pairs are formed, the rate of the reaction may be changed, due to the additional energy levels introduced by the spin-magnetic field interaction. Anyway, in order to have such kind of effects, you need an energy intensive process responsible for the radical pairs creation.