A NEW MULTILAYERED STRUCTURE FOR MULTILEVEL MAGNETORESISTIVE RANDOM-ACCESS MEMORY (MRAM) CELL

It is common practice to use two magnetic layers separated by a non-ma gnetic layer such as copper for the spin valve system. In this work, t hree magnetic layers(NiFe, NiFe/Co, and Co) are used to form a spin va lve and its magnetic properties are characterized. Due to the differen ce in the coercive field of the three magnetic layers, two plateaus ca n be obtained in IM-H and R-H curves. Each plateau plays as a recordin g level. According to the external magnetic fields,four distinguishabl e resistance states can be identified. The optimum preparative conditi on for the well defined four states have turned out to be NiFe(6 nm)/C u(2 nm)/NiFe(1.5 nm)/Co(4.5 nm)/Cu(2 nm)/Co(3 nm), where the multileve l MRAM is proved to be realized.