Ultrahigh efficient spin orbit torque magnetization switching in fully sputtered topological insulator and ferromagnet multilayers

Tuo Fan,Pham Nam Hai,Soichiro Nakano,Nguyen Huynh Duy Khang

doi:10.1038/s41598-022-06779-3

Abstract

Spin orbit torque (SOT) magnetization switching of ferromagnets with large perpendicular magnetic anisotropy has a great potential for the next generation non-volatile magnetoresistive random-access memory (MRAM). It requires a high performance pure spin current source with a large spin Hall angle and high electrical conductivity, which can be fabricated by a mass production technique. In this work, we demonstrate ultrahigh efficient and robust SOT magnetization switching in fully sputtered BiSb topological insulator and perpendicularly magnetized Co/Pt multilayers. Despite fabricated by the magnetron sputtering instead of the laboratory molecular beam epitaxy, the topological insulator layer, BiSb, shows a large spin Hall angle of θSH = 10.7 and high electrical conductivity of σ = 1.5 × 105 Ω−1 m−1. Our results demonstrate the feasibility of BiSb topological insulator for implementation of ultralow power SOT-MRAM and other SOT-based spintronic devices.

Highlights

Spin orbit torque (SOT) magnetization switching of ferromagnets with large perpendicular magnetic anisotropy has a great potential for the generation non-volatile magnetoresistive random-access memory (MRAM)
Since the spin-polarization of the pure spin current is perpendicular to the magnetization direction of the free magnetic layer, the spin torque is maximized and the magnetization can switch very fast (< ns) in SOT-MRAM with perpendicular magnetic anisotropy (PMA)[3]
Ultralow power SOT magnetization switching at room-temperature with current densities of the order of 1 05−106 Acm−2 have been demonstrated mostly in topological insulators (TIs)/magnetic layers whose magnetic anisotropy is very small, such as in a Bi2Se3/NiFe bilayer with nearly zero in-plane magnetic anisotropy[17], or in a Bi2Se3/CoTb bilayer with a small magnetization of 200 emu/cc and a PMA field of less than 2 kOe18

Summary

Introduction

Spin orbit torque (SOT) magnetization switching of ferromagnets with large perpendicular magnetic anisotropy has a great potential for the generation non-volatile magnetoresistive random-access memory (MRAM). In SOT-MRAM, a charge current flowing in a non-magnetic layer with large spin–orbit interaction can generate a pure spin current by the spin Hall effect.

Results

Conclusion