6.2 Double Exchange
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Fig. 6.2 Schematic explanation for the spin dependence of the hopping probability of the extra
electron in a background of unpaired electrons
Fig. 6.3 Double exchange mechanism proposed by Zener consisting in the simultaneous hopping
of an electron from center 1 to the bridge and from the bridge to metal 2
Fig. 6.4 Simple model to
describe electron hopping in
the background of unpaired
electrons, the orbitals are
mutually orthogonal
A rigorous description of electron hopping in the presence of other unpaired
electrons can be written down for the simple model system defined in Fig. 6.4.The
two electrons in the a 1 and b 1 orbitals provide a static background of unpaired
electrons for the mobile electron in the a 2 b 2 channel. Choosing M S =
1
2 , there are
24 ways to distribute the three electrons over the four orbitals, but only six of them