Compensation of orange-peel coupling effect in magnetic tunnel junction free layer via shape engineering for nanomagnet logic applications

We show that by avoiding fringing fields from synthetic antiferromagnet (SAF) structures and by engineering the shape of free layers, one can compensate the parasitic bias fields and have an unbiased magnetic tunnel junction (MTJ) free layer as an output for nanomagnet logic. Vibrating sample magnetometer measurements are used to investigate the switching behavior of nanoscale free layers of a PtMn/CoFe/Ru/CoFeB/MgO/CoFeB in-plane MTJ structure. The CoFe/Ru/CoFeB SAF structure of the measured MTJ stack is implemented in a shared configuration to eliminate fringing fields. In the absence of fringing fields, we experimentally observe a ferromagnetic “orange-peel” coupling field of 21 Oe between the nanoscale free layers and shared fixed layer. Micromagnetic simulations are performed to optimize the amount of slant on the edge of the free layer that compensates the 21 Oe bias field.