Angular Evolution of Magnetoresistance in Magnetic Tunnel Junctions With Synthetic Antiferromagnets

We investigate a magnetic tunnel junction (MTJ) with a pinned synthetic antiferromagnet (SAF) under the influence of an in-plane magnetic field applied at an angle to the SAF reference direction. The conductance of such an MTJ pillar deviates from a perfect cosine-like angle dependence primarily due to the presence of uniaxial anisotropy in the free layer and the finite values of the pinning field and RKKY coupling, which stabilize the SAF. We also consider other causes for the occurrence of angular error, such as the stray field from the SAF and the “orange peel” coupling effect. We develop a theory considering deviations of MTJ conductance up to the third harmonic based on the single domain (macrospin) approximation, allowing us to predict the angular error based on measured parameters at the thin-film level.