First demonstration of field-free perpendicular SOT-MRAM for ultrafast and high-density embedded memories

For the first time, we experimentally demonstrate the field-free switching in multi-pillar (MP) spin-orbit torque magnetic random-access memory (SOT-MRAM) devices, which are CMOS-compatible 300mm integrated perpendicular MTJs (p-MTJs). The field-free switching (FFS) is achieved by integrating an additional in-plane (IP) magnet layer below the conventional heavy metal layer, forming a hybrid spin source layer. The in-plane magnet contributes to additional unconventional spin-orbit torque, breaking the symmetry for field-free switching and leading to high SOT switching efficiency. We demonstrate ultrafast field-free switching with current pulses down to 0.3 ns, corresponding to a power consumption of 60 fJ/bit. Moreover, this FFS scheme is fully compatible with the standard integration process and the voltage-gated SOT (VG-SOT) switching in MP devices. Selective operations of independent write and read between multiple MTJs on a shared SOT track can also be achieved without external magnetic field. The FFS concept is scalable, agnostic to SOT material, and enables the reduction of the external periphery (i.e.: transistors). Thus, our proposed concept is advantageous for further improving the density and energy efficiency of SOT-MRAM technology.