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Particle Spin - how to cause change to direction

  1. Aug 31, 2014 #1

    len

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    Everywhere I read about the angular momentum / spin of electrons and how a 1/2 spin particle has a unique characteristic that you need to turn it 720 degrees in order to get it turned back to where it was before you started turning it.

    How exactly do people "turn" an electron in this fashion? I can't find anything anywhere that explains 'how' we are able to change the direction of the spin like that.

    Thanks
     
  2. jcsd
  3. Aug 31, 2014 #2

    atyy

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    Science Advisor

  4. Sep 1, 2014 #3
    There are various ways to create a controlled spin flip, depending on the system.

    The first way is just to wack your system with a giant magnetic field

    In ferromagnetic metals, you can use microwaves

    In direct bandgap semiconductors you can use microwaves or circularly polarized light

    For nuclear spins, you use radio waves.

    In oxides materials, there may be more exciting ways
     
  5. Sep 1, 2014 #4
    Are all those interactions essentially via magnetic fields? Is there any practical difference between spin and magnetic dipole moment?
     
  6. Sep 1, 2014 #5

    Nugatory

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    Staff: Mentor

    Yes, but....
    Yes. There are many more spin-related phenomena that have nothing to do with magnetic dipole moments.
     
  7. Sep 3, 2014 #6

    len

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    Thanks. What are some of the other spin-related phenomena? It's hard to find anything other than information about the magnetic dipole moment.

    I'm also wondering how angular momentum is actually detected or is it only surmised from observing the magnetic dipole?
     
  8. Sep 3, 2014 #7

    Nugatory

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    Staff: Mentor

    The pairing of electrons in orbitals, which is apparent from the structure of the periodic table of elements and accounts for pretty much all of modern chemistry is one example. The Pauli exclusion principle, without which the universe would be unimaginably different, is another.

    Conservation of angular momentum in reactions involving neutral particles is a bit less exciting than these but clearly shows that there can be spin without significant magnetic moment.
     
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