Abstract:
The frequency dependence of the electron-spin fluctuation spectrum,
P(Q), is calculated in the finite bandwidth model. We find that for Pd,
which has a nearly full d-band, the magnitude, the range, and the peak
frequency of P(Q) are greatly reduced from those in the standard spin
fluctuation theory. The electron self-energy due to spin fluctuations is
calculated within the finite bandwidth model. Vertex corrections are
examined, and we find that Migdal's theorem is valid for spin fluctuations in
the nearly full band. The conductance of a normal metal-insulator-normal
metal tunnel junction is examined when spin fluctuations are present in one
electrode. We find that for the nearly full band, the momentum independent
self-energy due to spin fluctuations enters the expression for the tunneling
conductance with approximately the same weight as the self-energy due to
phonons. The effect of spin fluctuations on the tunneling conductance is
slight within the finite bandwidth model for Pd. The effect of spin
fluctuations on the tunneling conductance of a metal with a less full d-band
than Pd may be more pronounced. However, in this case the tunneling
conductance is not simply proportional to the self-energy.
