Impact of local anisotropy modulation in one SAF sublayer on overall SAF-HFL switching

Determine how voltage-induced local modulation of magnetic anisotropy in a single sublayer of the synthetic antiferromagnetic hybrid free layer (SAF-HFL) used in perpendicular magnetic tunnel junctions affects the overall switching behavior of the SAF-HFL system.

Background

The paper studies voltage-gated spin–orbit torque MRAM devices that use a synthetic antiferromagnetic hybrid free layer (SAF-HFL). In such structures, two ferromagnetic layers are antiferromagnetically coupled via a spacer (e.g., Ru), and the device behavior under gate voltage involves the interplay of spin-transfer torque (STT), voltage-controlled magnetic anisotropy (VCMA), and Joule heating.

While VCMA is known to linearly modulate anisotropy at the CoFeB/MgO interface in single free-layer systems, SAF structures can exhibit complex switching pathways (two- or three-step) due to coupling and layer-specific anisotropies. The authors explicitly note that, prior to their study, it remained unclear how a local, voltage-induced modulation of anisotropy in one SAF sublayer influences the overall switching behavior of the coupled system. Their work investigates this question through simulations and experiments.