Influence of MTJ architecture on tunneling magnetoresistive effect for Al natural oxidation samples

Top-pinned and bottom-pinned magnetic tunnel junctions (MTJs) are manufactured using a 6-gun magnetron sputter and annealing process in an applied field of 3000 Oe by pure N protecting. The top-pinned MTJ has the architecture of glass/Ta35/spl Aring//NiFe200/spl Aring//CoFe10/spl Aring//Al(10/spl sim/20/spl Aring/)+oxidation/CoFe 30/spl Aring//MnIr150/spl Aring//Ta40/spl Aring/. While the bottom-pinned junction structure is glass/Ta35/spl Aring//NiFe20/spl Aring//MnIr70/spl Aring//CoFe30/spl Aring//Al(10/spl sim/20/spl Aring/)+oxidation/CoFeSO/spl Aring// NiFe45/spl Aring//Ta120/spl Aring/. For the top-pinned architecture, MTJ has a very small magnetoresistive (MR) ratio (2.35%) and the exchange field is approximately 0 Oe. The bottom-pinned MTJ however, has a large MR ratio (26%) and its exchange field is higher than 400 Oe, which makes it promising for applications in magnetic random access memory (MRAM) and some magnetic sensors.