Integration of BiSb Topological Insulator and CoFeB/MgO With Perpendicular Magnetic Anisotropy Using an Oxide Interfacial Layer for Ultralow Power SOT-MRAM Cache Memory
Ho Hoang Huy, Zhang Ruixian, Takanori Shirokura, Shigeki Takahashi, Yoshiyuki Hirayama, Pham Nam Hai
Abstract
BiSb topological insulator (TI) is attractive for the spin current source in spin–orbit torque (SOT) magnetoresistive random access memory (MRAM) thanks to its giant charge-to-spin conversion efficiency. However, the large spin Hall angles have been reported so far only in BiSb deposited on top of Co/Pt and Co/Tb multilayers. In a realistic SOT-MRAM application, it is essential to integrate BiSb to CoFeB/MgO junction with perpendicular magnetic anisotropy (PMA). Here, we report a large spin Hall angle of 2.8 in junctions of bottom BiSb and CoFeB/MgO with PMA using a CrOx interfacial layer, which is suitable for use in magnetic tunnel junctions (MTJs). We demonstrated SOT magnetization switching by a small current density of 3.1 MA/cm2 with a pulsewidth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50 ~\mu \text{s}$ </tex-math></inline-formula> , which is an order of magnitude smaller than that in heavy metals. Our work demonstrates the capability of integrating BiSb to CoFeB/MgO-based MTJ.