Spectroscopic evidence of high transport spin-polarization in ferromagnetic CuFeSb
We have measured the transport spin polarization in the itinerant ferromagnet CuFeSb by spin-resolved Andreev reflection spectroscopy. From the analysis of the Andreev reflection spectra within a modified Blonder-Tinkham-Klapwijk (BTK) formalism that includes Fermi-level spin polarization and the spectral broadening due to finite quasiparticle lifetime, we found that the intrinsic transport spin polarization in CuFeSb is approximately 50\%. This is significantly different from the half-metallic behaviour of CuFeSb as expected from band-structure calculation. We attribute this difference to possible difference in the Fermi velocities in the spin up and the spin down bands of CuFeSb.