What do Fe, Co, Ni - and possibly Gd - have in common to cause ferromagnetism and why is it seemingly absent in all other elements?

Question

I wonder whether the causes of ferromagnetism can be located purely in the electron shells and in cristaline structure or whether there is any aspect of it that is rooted in specific properties of the nucleus. If yes, what would that properties be and why would they be confined to Fe, Co and Ni. What would be their similarity to Gd which is ferromagnetic below 20°C. As to Neodymium, it is not ferromagnetic as an element, but only in combination i.e. as NdFeB (that is, it contains Iron) and even in ferromagnetic ceramics Iron needs to be present.