Net Magnetic Moment on Typical Ferromagnets

[sokrates]

What is the "net" magnetic moment per atom of a typical ferromagnet crystal ? I suspect the number will be different from those of "isolated" atoms because of band formation and spilling...
But I am not very sure, this could be wrong.

Is it 1 Bohr magneton per atom, 10 , 50 more ?

Do you have any ball park numbers on this or references?

 

[kanato]

Yes, they definitely can be different. A trivial example is Ag, which has a single unpaired electron in an isolated atom, but as metallic silver it is non-magnetic.

I don't know the experimental value, but from a DFT calculation the moment for Fe is 2.2$$\mu_B$$. In general, band formation (kinetic energy) competes with moment formation (exchange energy), so more localized orbitals (3d, 4f) tend to have narrower bandwidths and larger moments than less localized ones (4d, 5f).

For lanthanides, because the 4f states form very narrow bands, the 4f moment is about the same as the 4f moment for an isolated atom. IIRC this is true too for late actinides, past Am.

 

[sokrates]

I see...What about Cobalt and other alloys? Is there a tabulated reference where I can look all these up?

Thank you for the enlightening response,

 

[kanato]

I don't know, I only know the iron value because I recently did the calculation myself. Isolated atoms are pretty well characterized in any of the periodic table websites around the web, but I don't know of any similar database for solids.

 

[olgranpappy]

Yes, they definitely can be different. A trivial example is Ag, which has a single unpaired electron in an isolated atom, but as metallic silver it is non-magnetic.

I don't know the experimental value,

Turns out that it's a good deal lower than the DFT calculation. Around 0.8 Bohr magnetons, I think. Which is strange. Sorry, OP I don't know of a good general reference. Cheers,

Adam

but from a DFT calculation the moment for Fe is 2.2$$\mu_B$$. In general, band formation (kinetic energy) competes with moment formation (exchange energy), so more localized orbitals (3d, 4f) tend to have narrower bandwidths and larger moments than less localized ones (4d, 5f).

For lanthanides, because the 4f states form very narrow bands, the 4f moment is about the same as the 4f moment for an isolated atom. IIRC this is true too for late actinides, past Am.