Magnetic tunnel junctions(MTJs),as the seminal spintronic devices,are expected for applications in magnetoresistive sensors due to their large magnetoresistance(MR) and high field sensitivity.Two hybrid Co/insulator/ZnO:Co junctions were fabricated with two different barriers to investigate the magneto-transport properties.Experimental results indicate that,both Co/MgO/ZnO:Co and Co/ZnO/ZnO:Co junctions show the positive and nearly linear MR,and their tunnel magnetoresistances(TMR) are 21.8% and 13.6%,respectively,when the current is applied perpendicular to the film plane under the magnetic field of 2 T at 4 K.The nonlinearity of MR is less than 1% within the magnetic field(H) of 1 kOe < H < 12 kOe at low temperature,making them attractive as magnetoresistive sensors.The higher MR of Co/MgO/ZnO:Co junctions is due to the superior spin filtering effect and larger effective barrier height of the MgO barrier.This linear MR characteristic of Co/insulator/ZnO:Co structures shows a promising future on the applications of diluted magnetic semiconductors in magnetoresistive sensors.
