Investigating magnetic proximity effects in NiO/Pd with polarized neutron reflectometry

With polarized neutron reflectometry we investigated NiO/Pd heterostructures for the presence of a magnetic proximity effect, which is expected to produce an induced ferromagnetic moment in Pd. Using a specific isotope mixture of Ni in the preparation of NiO, the chemical contrast across the Pd/NiO interface was greatly suppressed, thus enhancing sensitivity to magnetic contrast at the reflecting interface. Despite enhanced sensitivity, no evidence for a proximity effect was observed. If present, the magnetic moment per Pd atom could not be more than 0.01μB, regardless of Pd layer thickness, crystalline interface orientation, and number of NiO/Pd bilayers.