Mn diffusion and the thermal stability of tunneling spin polarization

Abstract

We examine the role of Mn diffusion in the thermal stability of tunneling spin polarization P by directly measuring P of Al∕AlOx∕Co∕FeMn and Al∕AlOx∕Co90Fe10∕FeMn junctions using superconducting tunneling spectroscopy (STS). We confirm Mn diffusion in our junctions using x-ray photoelectron spectroscopy after an ultrahigh vacuum 500°C anneal. Surprisingly, and in contrast to the current belief, no drop in P is observed using STS. Therefore, though Mn diffuses significantly, it cannot be solely responsible for the drop in tunneling magnetoresistance observed after postdeposition anneals above 300°C.