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I Negative Magnetoresistance?

  1. Aug 20, 2016 #1
    A free electron gas would have zero magnetoresistance; it takes two carrier types to get ordinary magnetoresistance, which is always positive in sign.

    Beal-Monod and Weiner explain the negative magnetoresistance found in very dilute magnetic alloys, in terms of the spin-flip scattering of conduction electrons off the impurities.

    Their argument seems to be the following:

    Consider an electron scattering off of a magnetic impurity, in the presence of an applied field, in the case where μH<kT.

    An electron in initial state ki,↓ scatters into state kf,off of an impurity, whose spin is reduced to compensate. Conservation of energy gives ki=kf.The net change in electron energy should be -2μH.

    Since only electrons within kT of the Fermi Level can participate in scattering processes, they claim that this process should be forbidden. I don't see why.

    The original energy was at least εF±kT. The final energy should then be εF±kT-2μH. If μH<kT, then this should be guaranteed to remain within kT of the Fermi Level.

    What am I thinking about wrong? Thank you!

    (For what it's worth their exact words are "the final spin-up electron has a total energy (kinetic+Zeeman) less than εF by at least 2μH-kT." I just can't quite make the signs jibe or I am thinking about something wrong. Thanks!)
  2. jcsd
  3. Aug 25, 2016 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
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