Improvement of writing margin in MRAM with novel shape

We suggest a type of “goggle” cell shape and discuss its switching mechanism in comparison with conventional shapes such as rectangular and elliptical shapes. For the goggle shapes, the dependence of the switching characteristics on the saturation magnetization, the free layer thickness, and the aspect ratio was studied. We found that the “L”-like astroid curve with an enlarged writing margin could be obtained from a goggle shape, especially when the aspect ratio is smaller than 2. This seems to be closely related with the kink formation. We also found that the writing margin could be improved further as the saturation magnetization and thickness of the free layer was optimized.