Which way does the magnetism of the cubic iron struture point?

[Stickybees]

If you apply a field to iron the various domains move around, are the individual atoms of the FCC or BCC iron aligning with the field or does the unit cube tend to have an overall orientation which moves? If so then how would you know how the unit cubes are aligned relative to their poles?

Thanks if anyone has any insight :)

 

[M Quack]

There is a competition between magneto-crystalline anisotropy that favors alignment of the magnetic moments along a minimum energy crystal axis, and the Zeeman energy in the external field (if there is one).

In small external fields, the domains tend to have magnetic moments along their easy axis. Because of the high symmetry of cubic there are several symmetry-equivalent directions that all have the same intrinsic energy.

The microscopic magnetic structure can be studied by neutron scattering or x-ray diffraction. Techniques such as Moessbauer, muon spin rotation, and NMR can also provide addtional insight.

The magnetization process can be quite complicated, with domains growing and shrinking and sometimes "jumping" to a new direction because of pinning effects. This gives rise to the Barkhausen effect.

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