Reduction of Offset Field in Top-Pinned MTJ With Synthetic Antiferromagnetic Free Layer

We found that the offset field (H off ) of a top-pinned magnetic tunnel junction (MTJ) with a CoPd/Ru/Ta/CoFeB-synthetic antiferromagnetic (SAF) free layer can be reduced by controlling the exchange coupling energy (J ex ) value. A micromagnetic simulation was used to derive the direct relation between the J ex ) of a CoPd/Ru/Ta/CoFeB-SAF free layer and the H off ) of a top-pinned MTJ with the SAF free layer. In addition, we found that the J ex ) value can be controlled by changing the thickness of the Ta spacer between the CoPd and CoFeB layers. As a result, we fabricated a top-pinned MTJ with a SAF free layer that eliminated the offset field and made it possible to improve the thermal stability.