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Q & A: light through magnetic nano-torus

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Most recent answer: 10/25/2014
Q:
You have a nanotorus with a great magnetic moment (L Liu et al 2002 Phys. Rev. Lett. 88 217206). You shoot a beam of light through the center of the torus. What kind of physical reactions might we expect to occur in this scenario?
- Lauri Heikkinen (age 27)
Tampere, Finland
A:

Except for very high energy photons, electromagnetism in a vacuum is almost perfectly linear. That means that light propagates through a magnetic field just the same way it would through a zero-field region. In the particular case of those nano-tori, the field in the middle isn't even very big. They have a moment of around 100 Bohr magnetons, 10-18 emu, and linear dimensions that look like very roughly 10-6 cm. That means the field (roughly the moment per volume) is only around one Gauss, similar to the Earth's field. Even if my calculation is pretty far off, these fields are much smaller than those of an ordinary permanent magnet. There's another problem- the nano-tori are too small for a beam of ordinary visible light to fit through. You'd need x-rays to get a skinny enough beam.

Mike W.


(published on 10/25/2014)

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