When iron, cobalt and nickel are placed in weak fields they assume a large magnetic polarization. I was wondering if this weak field needs to be either diagmagnetic or paramagnetic field. My guess is that it is paramagnetic but not sure which paramagnets could be used. 'Weak field' is used in Linus Pauling's General Chemistry but in my textbook at school just 'magnetic field' is used and it also states that the size of the atom must be within the proper range. I don't know whether size is meant as atomic weight or atomic radii. Wonder if you could help me out with that one as well.