I'm hoping some one out there has as conceptual explanation as to the origin of Ferromagnetism. I know the magnetic fields are produced by moving charges and that atoms have moving electrons and hence display paramagnetism. Just a few pure elements have the ability to produce a permanent magnetic field, due to the cooperative alignment of the atomic magnetic moments. This is about where my understanding runs out of gas. Most sources I read simply say that the explanation for why certain substances produce this effect is "quantum mechanical in nature". I was hoping someone could give a little meaning to that last sentence.