Effect of the stray field profile on the switching characteristics of the free layer in a perpendicular magnetic tunnel junction

We show that the magnetic tunnel junction's coercivity (Hc) and anisotropy field (H-k) are linked to the stray field. This is shown by deliberately breaking the antiparallel configuration in the synthetic antiferromagnetic (SAF) reference layer to obtain changes to the stray field. Experimentally, H-c is larger in the low-H-o magnetic configuration with a normal SAF than in the high-H-o configuration with parallel-aligned SAF layers. Simulations reveal that the Hc reduction comes from the magnetization of the free layer tilting in-plane at the edge, which in turn is due to the large in-plane component of the stray field. Fitting the switching field distribution into the thermal activation model, we also show a close relationship between the thermal stability of the bi-stable switching, the anisotropy field (H-k), and the stray field. While it is possible to reduce H-o to zero with careful choice of the thickness of the SAF reference layers, the stray field at the edge cannot be fully eliminated. (C) 2015 AIP Publishing LLC.