I have read somewhere that magnetism of material comes from a spinning charge. Protons and neutrons are supposed to have spins too. But neutrons are not charged and yet they produce a magnetic field. Why? How do you count a spin of let's say an atom anyway? Is the total spin the sum of the spins of the neutrons, protons and electrons? Why is He-3 a fermion and He-4 a boson? Is it just because He-4 has an additional 1/2 spin from its additional proton?