Spin polarization measurements on polycrystalline strontium ruthenates using point-contact Andreev reflection

Point-contact Andreev reflection (PCAR) measurements were made on bulk polycrystalline Sr Ru 0.8 Ti 0.2 O 3 and Sr Ru 0.92 O 3 samples to determine the transport spin polarization. The parent compound Sr Ru O 3 undergoes ferromagnetic ordering at T C ∼ 160 K with relatively high spin polarization ( ∼ 60 % ) . For the Sr Ru 0.8 Ti 0.2 O 3 and Sr Ru 0.92 O 3 samples, a reduction in T C occurs. Moreover, our measurements indicate that the Sr Ru 0.8 Ti 0.2 O 3 system retains a high degree of spin polarization ( P ∼ 0.6 ) , similar to the parent compound. However, due to the insulating nature of Sr Ru 0.92 O 3 , the PCAR technique did not yield information on P . Instead, the data displayed nonlinear I - V consistent with the tunnelinglike spectra.