Why are Fe, Ni, Co ferromagnetic among metals?

[Trave11er]

What makes Fe, Co and Ni ferromagnetic compared to all other metals (with exception of Gd, Dy and some exotic alloys according to Wikipedia)? If other ferromagnetic metals just have lower Curie temperatures then why is it so?

Sub-question:
In pure metals is there any correlation in magnetic properties (paramagnetic/diamagnetic) vs number of electrons (odd/even) - analogously to N2 molecule with all electrons paired being diamagnetic, while O2 has unparied electrons and is paramagnetic.

 

[scoobmx]

It has to do with the density of states of the D band. The energy spacing between states is small enough that the cost of energy of moving some antiparallel electrons up to higher energy parallel states (because the lower energy states are already occupied) is met by the energy gained from interaction with the magnetic field. I can't answer your sub-question.

 

[M Quack]

The Wiki entry is a bit... suboptimally helpful, but I'm sure you can find better explanations of the Stoner model of ferromagnetism.

http://en.wikipedia.org/wiki/Stoner_criterion

To the sub-question:

Yes, this is somewhat related. However, since in these transition metals the magnetically active electrons reside in the D-shell, the dependence on the number of electrons is a bit more complicated than just odd/even. Again, the Wiki page leaves room for improvement, but also provides some hints and keywords to follow up upon.

http://en.wikipedia.org/wiki/Spin_states_(d_electrons)