Pac-man shaped magnetic tunnel junctions for SEU-resistant CMOS-based magnetic flip flops for space applications

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University of Alabama Libraries

Pac-man shaped magnetic tunnel junctions are proposed for CMOS-based magnetic flip flops for space applications. Micromagnetic simulation was performed on single layer elongated Pac-man shape, modified rectangular shape, and square shaped bilayer for magnetization process. The experimental effect of CoFe and IrMn thickness on the exchange field and coercivity of a Co₉₀Fe₁₀/Ir₂₀Mn₈₀ bilayer was studied. Metal mask process was used to fabricate rectangular shaped MTJ devices and the devices were characterized for magnetoresistance. In regards to micromagnetic simulation, the lowest coercivity of the elongated Pac-man element was found at an applied field direction at 45° with respect to the long axis of the element. Coherent switching of modified rectangular shapes was observed by simulation with a base height from 0.25 μm to 0.5 μm. In addition, simulation results of a 7 μm square shaped Ni₈₀Fe₂₀/antiferromagnetic bilayer are in fairly good agreement with experimental results for that of a 10 μm square shaped Ni₈₀Fe₂₀/Ir₂₀Mn₈₀ bilayer. Finally, CoFe thickness was found to be dominant in control of coercivity, while a combined effect of both CoFe and IrMn thickness has a major role in controlling of the exchange bias for a deposited CoFe/IrMn bilayer. The highest exchange of 87 Oe was achieved for Co₉₀Fe₁(8.5 nm)/Ir₂₀Mn₈₀ (17.5 nm). Magnetoresistance of four rectangular shaped MTJ device was measured to be 21% on average, but average resistance of the devices was 27 ohm. The resistance does not yet meet the targeted 10 kohm.

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Engineering, Electronics and Electrical, Engineering, Materials Science