First demonstration of field-free perpendicular SOT-MRAM for ultrafast and high-density embedded memories
Kaiming Cai, Giacomo Talmelli, Kaiquan Fan, S. Van Beek, Vaishnavi Kateel, Mohit Gupta, Maxwel Gama Monteiro, Mohamed Ben Chroud, Ganesh Jayakumar, A. Trovato, Siddharth Rao, Gouri Sankar Kar, Sébastien Couet
Abstract
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.