We propose to investigate with polarized neutron reflection (PNR) measurements the magnetic moment and interface properties of Co- and Fe-doped HfO2 thin films and undoped HfO2 barrier structures such as Co/HfO2/GaAs(100) and Fe/HfO2/GaAs(100), fabricated by dc and rf magnetron sputtering, varying both the thickness and doping of the oxide layer. Hafnium oxide presents an important opportunity to study an oxide with a ferromagnetic response at room temperature, and the growing interest in using this material to replace silicon oxide in integrated electronics also suggest a possibility of integrating spintronic applications with established industrial technology. The PNR experiment will let us establish the relative contributions of the dopant enriched surface layer and the rest of thin film to the total magnetic moment of this oxide.