  The spin polarization of Pt in Pt/NiFe2O4 and Pt/Fe bilayers is studied by
interface-sensitive x-ray resonant magnetic reflectivity to investigate static
magnetic proximity effects. The asymmetry ratio of the reflectivity was
measured at the Pt L3 absorption edge using circular polarized x-rays for
opposite directions of the magnetization at room temperature. The results of
the 2% asymmetry ratio for Pt/Fe bilayers are independent of the Pt thickness
between 1.8 and 20 nm. By comparison with ab initio calculations, the maximum
magnetic moment per spin polarized Pt atom at the interface is determined to be
$(0.6\pm0.1)\,\mu_{B}$ for Pt/Fe. For Pt/NiFe2O4 the asymmetry ratio drops
below the sensitivity limit of $0.02\,\mu_{B}$ per Pt atom. Therefore, we
conclude, that the longitudinal spin Seebeck effect recently observed in
Pt/NiFe2O4 is not influenced by a proximity induced anomalous Nernst effect.
