Low power spin–orbit torque switching in sputtered BiSb topological insulator/perpendicularly magnetized CoPt/MgO multilayers on oxidized Si substrate

Topological insulators (TIs) are promising for efficient spin current sources in spin–orbit torque (SOT) magnetoresistive random access memory (MRAM). However, TIs are usually deposited by molecular beam epitaxy on single crystalline III–V semiconductor or sapphire substrates, which are not suitable for realistic applications. Here, we studied SOT characteristics in sputtered BiSb topological insulator—Pt/Co/Pt—MgO heterostructures deposited on oxidized Si substrates, where Pt/Co/Pt trilayers have a large perpendicular magnetic anisotropy field of 4.5 kOe. We show that the BiSb layer has a large effective spin Hall angle of θSHeff = 2.4 and a high electrical conductivity of σ = 1.0 × 105 Ω−1 m−1. The magnetization can be switched by a small current density of 2.3 × 106 A cm−2 at a pulse width of 100 µs, which is 1 or 2 orders of magnitudes smaller than those in heavy metals. Our work demonstrates the high efficiency and robustness of BiSb as a spin current source in realistic SOT-MRAM.