Field-free spin-orbit torque switching of synthetic antiferromagnet through interlayer Dzyaloshinskii-Moriya interactions

Tailoring Interlayer Chiral Exchange by Azimuthal Symmetry Engineering

“…The maximum switching percentages (92% and 94% for type-T and SAF cases, respectively) occurred at φ D = 0° and 180°, consistent with the fact that φ D ∥ I pulse maximizes the z- oriented assist fields. This comparatively high switching percentage is an improvement over previous reports, possibly due to the enhanced H DMI , which overcomes the depinning fields or the Oersted fringing fields. , …”

“…In a system where magnetizations M 1 and M 2 are coupled by interlayer DMI, their energy density is expressed as Ê DMI = − D ·( M 1 × M 2 ), where M 1 and M 2 denotes the magnetizations’ unit vectors. Under a symmetry-breaking factor controlled by the Pt layer(s) atom flow direction, the vector D characterizes the strength and direction of interlayer DMI and should lie within the xy plane, , perpendicular to said symmetry breaking to satisfy the third Moriya rule . In the case of S1 samples where the two magnetizations are orthogonal, by taking M 1 and M 2 to be M Co and M CoFeB , respectively, Ê DMI gives rise to an effective DMI field H DMI = − D × M CoFeB acting on M Co with M CoFeB reciprocally experiencing an effective field of D × M Co .…”

“…This comparatively high switching percentage is an improvement over previous reports, possibly due to the enhanced H DMI , which overcomes the depinning fields or the Oersted fringing fields. 30,49 Azimuthal engineering presents opportunities for achieving a high H DMI and field-free switching. In addition, the counterwedge technique is an improvement over conventional wedge deposition since nominally, the antiparallel thickness gradients in discrete Pt layers cancel out with each other.…”

Field-Free Spin–Orbit Torque Switching via Oscillatory Interlayer Dzyaloshinskii–Moriya Interaction for Advanced Memory Applications

“…DMI relies on breaking inversion symmetry in the material and strong SOC. , When an in-plane symmetry-breaking element is added, long-range “interlayer” DMI (i-DMI) with a three-dimensional (3D) conformation has also been identified, where two ferromagnetic atoms exist in separate layers. − This chiral interlayer-coupling effect is pivotal in the realm of multilayered spintronic devices, particularly those employing dual PMA layers ,, or a combination of one PMA layer and an in-plane magnetized layer , (orthogonally magnetized systems). Groundbreaking research has already showcased the potential of i-DMI in driving current-induced magnetization switching in the absence of an external magnetic field. ,− For the field-free strategy, this chiral spin texture, especially in orthogonally magnetized systems, takes a different approach from utilizing the conventional symmetric exchange interaction, aiming to offer a larger zero-field SOT efficiency and a more robust field-free switching performance. These findings reveal new routes for real-world magnetic memory devices.…”