Talk:Spin wave

message: 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)
thread_title: Magnetostatic Waves

message: 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)
thread_title: Qualitative Description

message: 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)
replies: text: It doesn't meet the defining criterion for categorization, so I removed it. RockMagnetist(talk) 17:10, 22 March 2016 (UTC)
thread_title:  Heisenberg? 

message: 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)
replies: text: 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)
thread_title:  Quantum and Antiferromagnet spin waves 

message: 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  is the exchange energy, the operators  represent the spins at Bravais lattice points,  is the Landé -factor,  is the Bohr magneton and  is the internal field which includes the external field plus any "molecular" field.
 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,
:\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)
thread_title:  Definition of H?