Highly Energy-Efficient Spin-Orbit-Torque Magnetoresistive Memory with Amorphous W─Ta─B Alloys

Abstract

The spin Hall effect enables fast and reliable writing operations for next-generation spin-orbit-torque magnetoresistive random-access memories (SOT-MRAMs). To develop SOT-MRAMs; however, the spin Hall material should have a sufficiently low writing energy and high annealing stability for the semiconductor integration process. Thus far, none of the crystalline-based spin Hall materials are able to satisfy these requirements. Here, a promising solution for SOT-MRAMs is provided using amorphous W─Ta─B alloys. Even without a long-range crystal order, W─Ta─B alloys exhibit both large effective spin Hall angles up to 40% derived from a Ta substitutional doping and superior annealing stability (up to 400 °C) due to the addition of B, enabling them to satisfy both requirements. Nanoscale three-terminal SOT-MRAM cells are fabricated, and these are demonstrated to have high magnetoresistance ratios (up to 130%) and extremely low intrinsic switching current densities (down to 4 × 106 A cm−2). These results show that amorphous spin Hall materials can provide the key for realizing high-performance SOT-MRAMs.