Integration of BiSb Topological Insulator and CoFeB/MgO With Perpendicular Magnetic Anisotropy Using an Oxide Interfacial Layer for Ultralow Power SOT-MRAM Cache Memory

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.