Ti-alloyed β-W heterojunctions exhibiting spin-orbit torque switching at a wide operating temperature range

초록

Spin-orbit torque (SOT) switching has gained significant interest, particularly in the context of non-volatile embedded memory for advanced automotive vehicles. The study of temperature-dependent SOT switching, a less explored area, is crucial for developing automotive electronics Grade-0, which requires an ambient operating temperature range from -40 to 150 degrees C. These SOT devices demand substantial SOT efficiency to ensure a low operating current. Additionally, materials employed in these devices must be compatible with semiconductor fabrication. This study presents the first principles calculations to estimate the spin Hall conductivity (sigma SH) change of Ti-alloyed beta-phase W structures depending on the Ti composition. The calculation predicts the highest sigma SH value of -1461 (& hbar;/e) S/cm at Ti 12.5 at%. In addition, we fabricate beta-W-Ti (x at%) 5/Co40Fe40B20 0.9/MgO 1 (in nm) heterojunctions with various Ti compositions to confirm the above result experimentally. Under the controllable experimental condition, we observe the heterojunction with beta-W-Ti 11.5 at% exhibits an enhanced damping-like SOT efficiency of 0.54 (compared to 0.30 of pure beta-W) with longitudinal resistivity of 149.7 mu 52 center dot cm. The critical current density (Jc) reaches as low as 15.5 cm2. We also demonstrate that SOT switching is possible at ambient temperatures ranging from -55 to +150 degrees C.

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