Static Magnetic Proximity Effect in Pt Layers on Sputter-Deposited NiFe2O4 and on Fe of Various Thicknesses Investigated by XRMR

The longitudinal spin Seebeck effect is detected in sputter-deposited NiFe2O4 films using Pt as a spin detector and compared with the previously investigated NiFe2O4 films prepared by chemical vapor deposition. Anomalous Nernst effects induced by the magnetic proximity effect (MPE) in Pt can be excluded for the sputter-deposited NiFe2O4 films down to a certain limit, since X-ray resonant magnetic reflectivity measurements show no magnetic response down to a limit of 0.04 mu(B) per Pt atom comparable with the case of the chemically deposited NiFe2O4 films. These differently prepared films have various thicknesses. Therefore, we further studied Pt/Fe reference samples with various Fe thicknesses and could confirm that the MPE is only induced by the interface properties of the magnetic material.