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

Realizing robust field-free current-induced switching of perpendicular magnetization is of utmost importance to make spin–orbit torque (SOT) magnetic random-access memory (MRAM) possible. Diverging from the conventional field-free designs utilizing symmetric exchange interaction, this Letter explores the use of antisymmetric interlayer Dzyaloshinskii–Moriya interaction (i-DMI), which facilitates the emergence of noncollinear chiral spin configurations with wedge deposition. This work reveals a clear oscillatory behavior of the i-DMI strength with varying capping layer thickness, aligning with Bruno’s model. The strong i-DMI and sizable SOT efficiency observed in an optimized CoFeB/Pt(thick)/Co/Pt(thin) heterostructure result in a zero thermal critical switching current density of 1.67 × 1011 A/m2 and a thermal stability factor of 48.7, indicating the potential of such multilayer design for last-level cache memory applications. A counter-deposition method is also proposed to tackle the thickness variation issue caused by wedge deposition, offering a practical solution for implementing this field-free switching method.