Inverse magnetoresistance in magnetic tunnel junction with a plasma-oxidized Fe electrode and the effect of annealing on its transport properties

To understand the transport properties of Fe₃O₄ based magnetic tunnel junctions (MTJ), MTJs with a Fe₃O₄ electrode prepared by in situ plasma oxidation of a thin Fe film have been fabricated on oxidized silicon wafers with standard photolithography. High resolution transmission electron microscopy (HRTEM) was used to investigate the interface of the MTJs, and the magnetic and electrical transport properties of the MTJs were measured at different temperatures. TEM cross-section micrographs showed that the plasma oxidized Fe layer was directly in contact with the tunnel barrier (AlO_x), giving the predicted inverse magnetoresistance (MR). As the temperature was lowered, asymmetry in the MR and magnetic hysteresis (MH) curves appeared. A thin FeO phase at the interface seemed to produce this asymmetry. The effects of annealing on the transport properties are also discussed.