Proposal for Switching Current Reduction Using Reference Layer With Tilted Magnetic Anisotropy in Magnetic Tunnel Junctions for Spin-Transfer Torque (STT) MRAM

The design and statistical analysis of a magnetic tunnel junction with pinned-layer uniaxial anisotropy, slightly tilted with respect to the perpendicular magnetic anisotropy (PMA) of the free layer, are presented in the presence of thermally induced magnetic noise. The marginal tilting of the pinned-layer easy axis reduces the critical switching current density by almost 80%, as compared to a regular PMA device for a delay of 2 ns with a switching failure probability lower than 10^-9. Substantially lower switching current density in spin-transfer torque MRAM with tilted pinned-layer anisotropy enables the use of a higher resistance-area product with a thicker tunnel barrier that compensates for the tunneling-magnetoresistance rolloff due to the relative misalignment of free- and pinned-layer easy axes.