Field-Free Spin–Orbit Torque Switching Enabled by the Interlayer Dzyaloshinskii–Moriya Interaction

Abstract

Perpendicularly magnetized structures that are switchable using a spin current under field-free conditions can potentially be applied in spin−orbit torque magnetic randomaccess memory (SOT-MRAM). Several structures have been developed; however, new structures with a simple stack structure and MRAM compatibility are urgently needed. Herein, a typical structure in a perpendicular spin-transfer torque MRAM, the Pt/ Co multilayer and its synthetic antiferromagnetic counterpart with perpendicular magnetic anisotropy, was observed to possess an intrinsic interlayer chiral interaction between neighboring magnetic layers, namely, the interlayer Dzyaloshinskii−Moriya interaction (DMI) effect. Furthermore, using a current parallel to the eigenvector of the interlayer DMI, we switched the perpendicular magnetization of both structures without a magnetic field, owing to the additional symmetry breaking introduced by the interlayer DMI. This SOT switching scheme realized in the Pt/Co multilayer and its synthetic antiferromagnet structure may open a new avenue toward practical perpendicular SOT-MRAM and other SOT devices.

Engineering Spin Configurations of Synthetic Antiferromagnet by Controlling Long‐Range Oscillatory Interlayer Coupling and Neighboring Ferrimagnetic Coupling

“…Though the exact mechanism of this observed field-free SOT switching is unclear at present, the Dzyaloshinskii-Moriya interaction (DMI) should play an important role, because both the large difference in interfacial DMI of bottom and top magnetic layers and the additional interlayer DMI can lead to field-free SOT switching in SAFs. [38,39] An in-depth investigation is highly desired and the performance of field-free SOT switching can be further improved via some common approaches, such as exchange bias, interlayer exchange coupling, and tilted sputtering. [36,40,41] Finally, the SOT switching behavior of Type IV (Figure S4b, Supporting Information) is very similar to that of Type I.…”

Anisotropic Interlayer Dzyaloshinskii–Moriya Interaction in Synthetic Ferromagnetic/Antiferromagnetic Sandwiches

“…[24,25] Besides, some works reveal that IL-DMI is promising to facilitate field-free switching in spin orbit torque (SOT)-driven memory applications. [26,27] To further pave a wide pathway of spintronic devices applications utilizing IL-DMI, it is desirable to investigate the properties of IL-DMI and manipulate the IL-DMI.…”

Controlling the Interlayer Dzyaloshinskii–Moriya Interaction by Electrical Currents

“…Another route toward Hopfions is offered by the antisymmetric interlayer exchange interaction, which has been termed as RKKY-DMI or interlayer DMI (IL-DMI). − It favors spin canting between layers in the lateral direction and originates from in-plane symmetry breaking. This allows for a highly sought-after tuning mechanism for 3D magnetic textures, which could stabilize such structures in magnetic multilayers without confinement.…”

“…This would allow for writing and deleting operations, which are necessary when the different magnetic textures are employed as bits. Furthermore, the IL-DMI can allow for field-free switching as recent studies have shown. , This pure electrical switching facilitated by the IL-DMI offers new possibilities for spintronic devices while the IL-DMI is relatively simply induced by an oblique sputtering technique or a magnetic field during deposition . Conventionally, the strength of both DMI and IL-DMI is set during sample growth.…”

“…The current-induced IL-DMI also opens new possibilities for pure-electrical field-free switching. As field-free switching has been observed in samples with IL-DMI, , it is up to further studies to investigate the relation between current-induced IL-DMI and field-free switching.…”