A spinwave among
precessing magnetic dipoles
Spinwaves in 2 dimensions
A spinwave (or its quasi-particle equivalent, the magnon) is "an elementary excitation of a magnetic system which is usually long-range-ordered, such as a ferromagnet." (Ref: http://www.accessscience.com) search words="magnon".
For example, in a sample of pure iron, it is the unpaired electrons within the atomic lattice that are responsible for the material's magnetic properties. These electrons have spin and an associated magnetic moment creating individual magnetic dipoles through each electron's spin axis. Each electron's spin axis also precesses like a gyroscope and spinwaves propagate through these precessing magnetic dipoles of the electrons as their individual magnetic fields interact with each other. In other magnetic materials a combination of both axial and orbital electron spin can create magnetism if the combination is not compensated for by equal and opposite combined spins of other electrons. Spinwaves propagate through the precessions of these uncompensated spins. Spinwaves can also propagate through uncompensated nuclear spins but the magnetic moments and coupling between spins is weaker than with electron spins.
In real life, spinwaves can propagate in all directions in a magnetic material and not in just 1 dimension or just across a 2 dimensional surface as the diagrams show. But magnetic materials can be engineered to promote the development of coherent spinwaves in preferred directions.
Compensated spins will also precess, but due to their mutual compensation, electromagnetic radiation to/from these compensated spins is not detectable with typical equipment for measuring electromagnetic radiation.
See an example of an atypical device for measuring atypical electromagnetic radiation to/from compensating electron spins on
page 5 of this presentation. You may recognize this device if you have ever studied the presentations from Bob Lazar who claimed to have worked on antigravity technology.
Read more about spinwaves from wikipedia https://en.wikipedia.org/wiki/Spin_wave or stay here and click "Read more ..." below to learn about spinwave lasers, power generation and much more.
UPDATE Oct. 5th, 2020: Here is an excellent Youtube animation of a spinwave: https://www.youtube.com/watch?v=cBo91aGls0E
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