Talk:Spin wave

Magnetostatic Waves[edit]

No explicit reference to long range magnetic dipole interactions is made, which can be imporant for long wavelength magnetic waves and ferromagnetic resonance. I propose including a discussion of magnetostatic waves; classic references include L.R. Walker, Physical Review Vol. 105 p390 (1957) and J.R. Eshbach and R.W. Damon, Physical Review Vol 116 p1208 (1960). Magnetic monopole (talk) 01:15, 11 May 2009 (UTC)[reply]

Qualitative Description[edit]

Wow, this is a fairly exhaustive mathematical analysis of spin waves for Wikipedia. However, I must say that this article requires at least a minimal qualitative description of what spin-waves are. The first sentence of the theory is "The simplest way of understanding spin waves is to consider the Hamiltonian". Surely there is a more gradual approach to this topic than to talk about Hamiltonians and eigenstates right away. I would add to this article but am taking a Magnetics class just now and am not fully confident of my understanding. Additional qualitative description would be appreciated.--vlado4 05:56, 8 October 2007 (UTC)[reply]

Alison Chaiken 22:30, 8 September 2005 (UTC): I have lots more to add to this article but am out of time at the moment.[reply]

Alison Chaiken 16:52, 19 September 2005 (UTC): I'm sure that there are inelastic neutron scattering facilities that I've overlooked in my list. Please correct this oversight if you know of more. Neutron scattering is not my field![reply]

Heisenberg?[edit]

This edit has just categorised these under Category:Werner Heisenberg. Is that justified? They're not one of Heisenberg's better known discoveries, but then nor are they my field. Thoughts? Andy Dingley (talk) 11:33, 22 March 2016 (UTC)[reply]

It doesn't meet the defining criterion for categorization, so I removed it. RockMagnetist(talk) 17:10, 22 March 2016 (UTC)[reply]

Quantum and Antiferromagnet spin waves[edit]

Should we add the quantized version of magnon calculation? Should we add the antiferromagnet case? Just a thought MaoGo (talk) 21:16, 8 February 2017 (UTC)[reply]

Yes please :) It's (imo) easier to understand the semiclassical approach; I came here to try to understand the purely quantum mechanical one, which is a bit harder in its details. Miguelmurca (talk) 13:41, 19 July 2019 (UTC)[reply]

Definition of H?[edit]

Under

he simplest way of understanding spin waves is to consider the Hamiltonian ${\mathcal {H}}$ for the Heisenberg ferromagnet:

${\mathcal {H}}=-{\frac {1}{2}}J\sum _{i,j}\mathbf {S} _{i}\cdot \mathbf {S} _{j}-g\mu _{B}\sum _{i}\mathbf {H} \cdot \mathbf {S} _{i}$

where $J$ is the exchange energy, the operators $S$ represent the spins at Bravais lattice points, $g$ is the Landé $g$ -factor, $μ B$ is the Bohr magneton and $H$ is the internal field which includes the external field plus any "molecular" field.

$H$ is given as including the molecular field, but (unless I'm missing something), the molecular field should be an alternative representation to the first term (thus modelling the exchange as a field)? From Oxford's book on Magnetism by Blundell,^[1]

${\hat {\mathcal {H}}}=-\sum _{ij}J_{ij}\mathbf {S} _{i}\cdot \mathbf {S} _{j}+g\mu _{B}\sum _{j}\mathbf {S} _{j}\cdot \mathbf {B}$

where B is the applied magnetic field, we define an effective molecular field

$\mathbf {B} _{\mathrm {mf} }=-{\frac {2}{h\mu _{B}}}\sum _{j}J_{ij}\mathbf {S} _{j}$

[... such that ...]

${\hat {\mathcal {H}}}=g\mu _{B}\sum _{i}\mathbf {S} _{i}\cdot (\mathbf {B} +\mathbf {B} _{mf})$

Is it possible to have a molecular field (as opposed to an external one) that isn't a model for exchange interaction? Otherwise, maybe the «plus any "molecular" field» bit could be removed.

Miguelmurca (talk) 14:13, 18 July 2019 (UTC)[reply]

^ Blundell, Stephen (2001). Magnetism in Condensed Matter (1st ed.). Oxford, New York: Oxford University Press. pp. 85, 86. ISBN 0 19 850592 2.

[1] Blundell, Stephen (2001). Magnetism in Condensed Matter (1st ed.). Oxford, New York: Oxford University Press. pp. 85, 86. ISBN 0 19 850592 2.

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