Semi-Classical Treatment of Spin Waves in Antiferromagnetic Systems

  • Thread starter thoughtgaze
  • Start date
  • Tags
    Spin Waves
In summary, Anderson argues that a semi-classical treatment is appropriate in the AF case where S->infinity is a well-defined limit.
  • #1
thoughtgaze
74
0
Hey,

can anyone point me to some useful reading material on the semi-classical treatment of spin waves for the antiferromagnetic case? Thanks.
 
Physics news on Phys.org
  • #2
P W Anderson, Concepts in solids, World Scientific, Singapore, 1997
 
  • #3
DrDu said:
P W Anderson, Concepts in solids, World Scientific, Singapore, 1997
great book...

though not quite sure whether it treats spin waves semi-classically..

edit: in fact I just checked it and the treatment is completely quantum-mechanical.
 
  • #4
Can you treat spin-waves in AF semi-classically? I seem to think that you don't get a reasonable limit as the spin S -> infinity --- it oscillates in behaviour on S being a half-integer and S being integer. (And that's ignoring possible lattice frustration.)
 
  • #5
Yes, you can.

Just like you can semi-classically treat, phonons, electrons, etc..

you can treat "magnons" semi-clasically too.

Semi-classical,in this context, means an input from quantum mechanics (like dispersion relations, density of states, or effective mass which more or less give equivalent information) accompanied with classical dynamics equations.
 
  • #6
No, I mean does it make for a good approximation (of course you *can* always just postulate a classical particle + corrections). Certainly in 1D spin-1/2 AF do not have spin waves as an elementary particle, since the spinon and holons are deconfined; in this case, I would say that a semi-classical treatment of spin-waves is not appropriate. Usually, in the ferromagnetic case, things are justified because S->infinity is a well defined limit in which we really do get spin waves, and we can argue for a 1/S expansion, in which case the leading order corrections can be seen as interactions. In the AF case, this can not be done analogously.
 
  • #7
sokrates, I had a look at my copy again. Methinks that Anderson uses in the last chapter "anti-ferromagnetism and broken symmetry" basically a semi-classical approximation, especially the decoupling of the equation of motion, where he replaces the cross product of spin operators by their mean values, neglecting quantum fluctuations is a semi-classical argumentation.
 
  • #8
DrDu said:
sokrates, I had a look at my copy again. Methinks that Anderson uses in the last chapter "anti-ferromagnetism and broken symmetry" basically a semi-classical approximation, especially the decoupling of the equation of motion, where he replaces the cross product of spin operators by their mean values, neglecting quantum fluctuations is a semi-classical argumentation.

Maybe semi-classical is used in a different context, here. I don't know what the OP needed. I am familiar with the usage I said above.

Just wondering, is Anderson, himself, saying it's a semi-classical treatment?
 
  • #9
genneth said:
No, I mean does it make for a good approximation (of course you *can* always just postulate a classical particle + corrections). Certainly in 1D spin-1/2 AF do not have spin waves as an elementary particle, since the spinon and holons are deconfined; in this case, I would say that a semi-classical treatment of spin-waves is not appropriate. Usually, in the ferromagnetic case, things are justified because S->infinity is a well defined limit in which we really do get spin waves, and we can argue for a 1/S expansion, in which case the leading order corrections can be seen as interactions. In the AF case, this can not be done analogously.

I could not follow your argument. But "we can treat de-localized Bloch electrons as semi-classical particles using a band diagram coupled with Boltzmann equation" is what I really meant.
 

1. What are antiferromagnetic spin waves?

Antiferromagnetic spin waves are collective oscillations of the individual magnetic moments in an antiferromagnetic material. These waves are caused by the interactions between neighboring spins and can propagate through the material, similar to how sound waves travel through air.

2. How are antiferromagnetic spin waves different from ferromagnetic spin waves?

Antiferromagnetic spin waves differ from ferromagnetic spin waves in their direction of rotation. In ferromagnetic materials, all spins are aligned in the same direction, resulting in waves that rotate in the same direction. In antiferromagnetic materials, neighboring spins are aligned in opposite directions, causing the waves to rotate in opposite directions as well.

3. What are the applications of antiferromagnetic spin waves?

Antiferromagnetic spin waves have potential applications in data storage and processing, as they can be used to transfer and manipulate information in a non-destructive way. They can also be used in spintronic devices, such as sensors and memory elements.

4. How are antiferromagnetic spin waves studied?

Antiferromagnetic spin waves can be studied using various experimental techniques, including neutron scattering, spin resonance, and Brillouin light scattering. Theoretical models and simulations are also used to understand the behavior of these waves in different materials.

5. Can antiferromagnetic spin waves be controlled?

Yes, antiferromagnetic spin waves can be controlled by applying external magnetic fields or by using spin-polarized currents. These methods can change the properties of the spin waves, such as their frequency and propagation direction, allowing for potential applications in spin-based devices.

Similar threads

  • Atomic and Condensed Matter
Replies
6
Views
1K
  • Atomic and Condensed Matter
Replies
2
Views
2K
  • Atomic and Condensed Matter
Replies
2
Views
1K
Replies
1
Views
1K
  • Atomic and Condensed Matter
Replies
2
Views
1K
  • Atomic and Condensed Matter
Replies
1
Views
1K
  • Atomic and Condensed Matter
Replies
4
Views
848
  • Advanced Physics Homework Help
Replies
1
Views
947
  • Atomic and Condensed Matter
Replies
3
Views
2K
Replies
6
Views
659
Back
Top