Effects of interfacial Fe electronic structures on magnetic and electronic transport properties in oxide/NiFe/oxide heterostructures

We report that the magnetic and electronic transport properties in oxide/NiFe(2 nm)/oxide film (oxide = SiO2, MgO or HfO2) are strongly influenced by the electronic structure of NiFe/oxide interface. Magnetic measurements show that there exist magnetic dead layers in the SiO2 sandwiched film and MgO sandwiched film, whereas there is no magnetic dead layer in the HfO2 sandwiched film. Furthermore, in the ultrathin SiO2 sandwiched film no magnetoresistance (MR) is detected, while in the ultrathin MgO sandwiched film and HfO2 sandwiched film the MR ratios reach 0.35% and 0.88%, respectively. The investigation by X-ray photoelectron spectroscopy reveals that the distinct interfacial redox reactions, which are dependent on the oxide layers, lead to the variation of magnetic and transport properties in different oxide/NiFe/oxide heterostructures.