Using the technique of ballistic electron magnetic microscopy, we have studied the spin-asymmetry of transmission of hot electrons in Fe, for which a recent ab initio calculation has shown that the inelastic lifetime is similar for majority and minority spin. Nevertheless, using a spin-valve structure of ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}∕\mathrm{Au}∕\mathrm{Fe}$, we find that the attenuation length of hot electrons in Fe at $1.2–1.6\mathrm{eV}$ is a factor of 4 larger for the majority spin. We argue that this large spin-asymmetry arises from the spin dependence of the group velocity, rather than the lifetime.

• Received 30 July 2007

DOI:https://doi.org/10.1103/PhysRevB.76.140407