Most stable nuclei are magnetic

[vickyc]

Hi,
I'm in my last year of school and part of my A-Level is on nuclear physics. We've recently studied binding energy and I noticed that the elements with the highest binding energy per nucleon (the most stable nuclei) are magnetic - iron, cobalt and nickel. Are binding energy and magnetism linked, or is this just a coincidence?

 

[Vanadium 50]

It's a coincidence. The other two ferromagnetic elements are gadolinium and dysporosium. Also, there are magnetic and non-magnetic steels, and of course the nuclei are exactly the same.

 

[arivero]

It's a coincidence. The other two ferromagnetic elements are gadolinium and dysporosium. Also, there are magnetic and non-magnetic steels, and of course the nuclei are exactly the same.

Now, the coincidence could have be given in a more precise form by looking at Curie Temperatures. Here in Kelvin:

Co 1388
Fe 1043
Ni 627
Gd 292
Dy 88
Li <1

From time to time, ferromagnetism of Pd or even Pt is reported by some research.

This periodic table clarifies the role of chemical structure
http://www.msm.cam.ac.uk/doitpoms/tlplib/ferromagnetic/images/FigureE.gif
http://www.msm.cam.ac.uk/doitpoms/tlplib/ferromagnetic/printall.php

Actually, the fact that there is a shell model also for nuclear stability could have some role justifying the coincidence, could it? The proton number where the lower nuclear shells close to stability is also the electron number where electron subshells allow for ferromagnetic magnetic dipoles. In this sense, it should be only a mathematical coincidence, with nuclear spin playing no role.

 

[bcrowell]

I think arivero has it right.

Nuclear structure relates to the magnetic properties of the *nucleus*. Since the nucleus is smaller than the electron cloud by a factor of 10⁵, we expect the nuclear contribution to the atom's magnetic dipole moment to be smaller by that factor.

In the case of an even-even nucleus, the dipole moment has to vanish by symmetry, because the angular momentum of the ground state is zero, so there is no preferred axis. So for instance ⁵⁶Fe has zero nuclear magnetic dipole moment.

 

[Rajini]

Hi,
this information may be useful..
⁵⁷Fe has nuclear magnetic dipole moment.

 

[bcrowell]

Hi,
this information may be useful..
⁵⁷Fe has nuclear magnetic dipole moment.

Yes, any odd nucleus will have a dipole moment, but it will not contribute significantly to the magnetic properties of the material, for the reasons given in #4.