[Paper Review] Room-temperature perpendicular magnetization switching through giant spin-orbit torque from sputtered BixSe(1-x) topological insulator material

Mahendra DC, Mahdi Jamali+10 more|arXiv (Cornell University)|Mar 10, 2017

Magnetic properties of thin films52 references152 citations

TL;DR

Demonstrates room-temperature perpendicular magnetization switching driven by an exceptionally large spin-orbit torque from sputtered BixSe(1-x) topological insulator, achieving a record-high spin Hall angle and low switching current in a bilayer system.

ABSTRACT

The spin-orbit torque (SOT) arising from materials with large spin-orbit coupling promises a path for ultra-low power and fast magnetic-based storage and computational devices. We investigated the SOT from magnetron-sputtered BixSe(1-x) thin films in BixSe(1-x)/CoFeB heterostructures by using a dc planar Hall method. Remarkably, the spin Hall angle (SHA) was found to be as large as 18.83, which is the largest ever reported at room temperature (RT). Moreover, switching of a perpendicular CoFeB multilayer using SOT from the BixSe(1-x) has been observed with the lowest-ever switching current density reported in a bilayer system: 2.3 * 105 A/cm2 at RT. The giant SHA, smooth surface, ease of growth of the films on silicon substrate, successful growth and switching of a perpendicular CoFeB multilayer on BixSe(1-x) film opens a path for use of BixSe(1-x) topological insulator (TI) material as a spin-current generator in SOT-based memory and logic devices.

Motivation & Objective

• Motivate the use of materials with large spin-orbit coupling to enable ultra-low power, fast magnetic storage and logic.
• Quantify the spin-orbit torque efficiency and switching behavior in BixSe(1-x)/CoFeB heterostructures.
• Demonstrate room-temperature perpendicular magnetization switching in a TI-based bilayer system.

Proposed method

• Fabricate magnetron-sputtered BixSe(1-x) thin films and form BixSe(1-x)/CoFeB heterostructures on silicon substrates.
• Measure spin-orbit torque using a dc planar Hall method.
• Extract the spin Hall angle from the planar Hall data.
• Demonstrate switching of a perpendicular CoFeB multilayer induced by SOT at room temperature.
• Compare switching current density with known benchmarks in bilayer systems.

Experimental results

Research questions

• RQ1 What is the magnitude of the spin Hall angle in sputtered BixSe(1-x) and how does it behave at room temperature?
• RQ2 Can SOT from BixSe(1-x) induce reliable perpendicular magnetization switching in CoFeB multilayers at RT?
• RQ3 What is the lowest switching current density achievable in this TI/ferromagnet bilayer system?
• RQ4 Do these films exhibit smooth surfaces and scalable growth on silicon substrates for device integration?

Key findings

• Spin Hall angle up to 18.83 at room temperature, the largest reported in RT for this class of materials.
• Room-temperature switching of a perpendicular CoFeB multilayer driven by SOT from BixSe(1-x).
• Lowest-ever switching current density reported in a bilayer system: 2.3 × 10^5 A/cm^2 at RT.
• Giant SOT with easy growth on silicon substrates and smooth film surfaces, enabling TI-based spin-current generation for memory/logic devices.