A Novel Transistor Free Design of SOT-MRAM Written by Unipolar Current with Record Bit Cell Size (15F²)

Spin-orbit torque (SOT)-MRAM bit cell takes up a large area (~75F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) due to the two access transistors architecture. To address this problem, our innovative spin-orbit torque magnetic tunnel junction (SOT-MTJ) device, which operates through unipolar current writing, facilitates the replacement of transistors with diodes in a single bit cell (2D-1M), resulting in a remarkably compact size of ~24F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. In addition, we designed a 5D-4M structure to further reduce the area to 15F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. Four MTJs of the 5D-4M structure are on a shared SOT track and written simultaneously by unipolar current due to voltage controlled magnetic anisotropy (VCMA) effect, leading to energy consumption reduction of 37.5%.