Negative spin-polarization of SrRuO3

We have made Meservey-Tedrow style spin-polarized tunneling measurements on SrRuO3, using a SrTiO3 barrier. In contrast to all other materials measured with this technique, we found the spin polarization to be negative, P = -9.5%. This makes it possible to test the generalized Julliere model for a negatively spin-polarized electrode, by measuring the magnetoresistance of a La0.7Sr0.3MnO3/SrTiO3/SrRuO3 tunnel junction. The generalized Julliere theory predicts it should be inverse.