Spin-Orbit-Torque Switching in 20-nm Perpendicular Magnetic Tunnel Junctions

Abstract

Magnetization switching utilizing the spin orbit torque of heavy metals is a promising alternative to spin transfer torque for a faster and more energy efficient write mechanism for magnetic random-access memory. We report spin orbit torque switching in a 20 nm diameter, CoFeB-MgO-based perpendicular magnetic tunnel junctions with a thermal stability factor of ~47. Conductive atomic force microscopy was used to measure the tunnel magnetoresistance before and after current pulses through the heavy metal underlayer, and magnetostatic shifts in the minor loops provided evidence of spin orbit torque switching. Comparison of estimated critical current densities and write energies suggest that spin orbit torque can be used as an effective switching mechanism for small and thermally stable perpendicular magnetic tunnel junctions. I.

Field-Free Magnetization Switching in a Ferromagnetic Single Layer through Multiple Inversion Asymmetry Engineering

“…In recent years, using spin–orbit torque (SOT)-induced magnetization switching to accomplish fully electrical manipulation of perpendicular magnetization has become a promising solution for ultra-low-power, nonvolatile memory and logic devices. − Compared to already commercialized spin-transfer torque magnetic random access memory, the SOT is capable of providing significantly increased stability, improved energy efficiency, and better scalability. As a result, SOT-induced magnetization switching has been studied in heavy metal/ferromagnetic (HM/FM) bilayers, − topological insulators/FM, − transition metal dichalcogenides, ferrimagnetic and antiferromagnetic systems, − and single-layer magnetic films. − Among these studies, SOT-induced field-free magnetization switching is one of the most pressing issues in SOT-based memory and logic applications.…”

Modulation of Heavy Metal/Ferromagnetic Metal Interface for High‐Performance Spintronic Devices

“…The p‐SOT‐MTJ composed of a Ta (20 nm)/CoFeB (1 nm)/MgO/CoFeB (1.5 nm)/Ta (5 nm)/Ru (7 nm) stack generates a TMR ratio of 55%, which is equivalent to that of another p‐SOT‐MTJ with Ta layers and SAF layers . Recently, a remarkable TMR ratio of 128% has been reported in the Ta/CoFeB/MgO p‐SOT‐MTJ stack with a thermal stability factor of ≈47 . The high TMR ratio can be attributed to the careful control of the oxidation level, which induces the strong PMA.…”

Spin–Orbit Torque Switching of a High-Quality Perpendicularly Magnetized Ferrimagnetic Heusler Mn3Ge Film

“…Current-driven magnetization switching via the spin–orbit interaction-induced spin Hall effect offers a competitive alternative to the spin-transfer torque for magnetic random access memory (STT-MRAM), which is an emerging nonvolatile memory technology. − Current-induced spin–orbit torque (SOT) switching has advantages of decoupling the writing and reading processes and fast writing speed due to the absence of incubation time as in STT-MRAM. − In heavy metal (HM)/ferromagnetic metal (FM) heterostructures, the spin-up and spin-down electrons are deflected in opposite directions in the HM with a strong spin–orbital coupling. Therefore, a spin current is injected into the adjacent FM layer and exerts a spin torque on its magnetization. − To date, in most HM/FM heterostructures, perpendicularly magnetized anisotropy (PMA) magnets have been limited to interfacial PMA, which requires an ultrathin ferromagnetic layer. − , However, the interfacial nature of magnetic anisotropy in these SOT heterostructures remains a challenge for practical applications as it cannot maintain a sufficiently large energy barrier against thermal fluctuations.…”