Larmor precession and magnetic ordering

AI Thread Summary
Larmor precession describes the behavior of atomic magnetic moments in a magnetic field, but in ordered magnets like ferromagnets, this phenomenon is less discussed. The magnetic moments may appear "frozen" due to interactions with crystal fields or may precess uniformly in the same direction. The breaking of rotational symmetry in a compound can quench angular momentum, affecting the behavior of these moments. This concept relates to the energy levels of orbitals influenced by crystal field interactions. The discussion highlights the connection between Larmor precession and applications such as Magnetic Resonance Imaging.
DeathbyGreen
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Homework Statement


When we speak about Larmor precession we refer to atomic magnetic moments precessing in a magnetic field. In ordered magnets, such as ferromagnets, I never hear about larmor precession anymore. Are the magnetic moments frozen due to interactions with the surrounding crystal fields? Or all the moments precessing in the same direction? This isn't a homework question, just one I was thinking about and unable to find a good answer for.
 
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Indeed. The moments do not even need to be ordered. In a compound, the rotational symmetry is broken, and this often leads to the angular momentum being quenched.
 
By rotational symmetry being broken, do you mean that the crystal field interaction forces the eg and t2 orbitals into different energy levels? I'm not to familiar with symmetry breaking but I'll try and read into it.
 
Yes, that is in cubic symmetry. Angular momentum is not a good quantum number unless there is rotational symmetry.
 
DeathbyGreen said:
I never hear about larmor precession anymore
Ahh...Magnetic Resonance Imaging owe's its existence to this!
 

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