Device applications of the giant direct and inverse spin Hall effect in BiSb topological insulator

BiSb is a topological insulator with high electrical conductivity and a giant spin Hall effect at room temperature, making it a promising candidate for various spin-orbit torque (SOT) device applications. Over the past five years, we have demonstrated proof-of-concept of physical vapor deposition of high quality BiSb thin film, integration of BiSb / perpendicularly magnetized ferromagnetic multilayers with high electrical conductivity (~1.5×10⁵ Ω⁻¹m⁻¹) and a giant spin Hall angle (> 10), ultralow current (10⁴ ~ 10⁵ A/cm²) and ultrafast (~1 ns) switching of ferromagnetic multilayers by BiSb, integration of BiSb to CoFeB/MgO/CoFeB-based magnetic tunnel junction with relatively high tunneling magnetoresistance ratio and low switching current density. For practical device applications, we have collaborated with storage vendors such as SamSung and Western Digitals to develop several fundamental technologies utilizing the giant spin Hall effect of BiSb for high-level SOT-MRAM cache memory and SOT magnetic sensing device for read head sensor in hard disk drive. We show that BiSb-integrated SOT magnetic sensor has a giant inverse spin Hall angle (~61), which is good enough for use in 4 Tbit/inch² magnetic recording technology. Furthermore, we demonstrated that BiSb after 400°C annealing and recrystallization can still have high enough spin Hall angle for ultralow current switching in SOT-MRAM. Our works open the way for SOT device applications of BiSb topological insulator.