Magnetic Memory Bits with Perpendicular Magnetization Switched By Current-Induced Spin-Orbit Torques

Summary

UCLA researchers in the Department of Electrical and Computer Engineering have developed a novel spin-orbit-torque (SOT)-controlled magnetic random access memory driven by in-plane currents.

Background

Magnetization switching by current-induced spin-orbit torques (SOTs) has been attracting great attention for its potential applications in ultra low power memory and logic devices. The use of SOTs in nonmagnetic metal/ferromagnet/insulator structures allows for a significantly lower write current compared to regular spin-transfer-torque (STT) devices. It can also greatly improve the energy efficiency and scalability for new SOT-based devices such as magnetic random access memory (SOT-MRAM). However, practical use of SOT effects is limited by its requirement of an in-plane external magnetic field, in order to switch ferromagnets with a perpendicular (out-of-plane) magnetization.

Innovation

Researchers at UCLA have developed a novel nonmagnetic metal/ferromagnet/insulator structure which provides a SOT, resulting in zero-field current-induced switching of perpendicular magnetization. The device consists of a ferromagnetic free layer, a ferromagnetic fixed layer, a dielectric tunnel barrier, and a high-spin-orbit-coupling material, and has a structural mirror asymmetry along the in-plane direction. The lateral structural asymmetry effectively replaces the role of the external in-plane magnetic field and eliminates the use of external magnetic fields, bringing SOT-based spintronic devices such as SOT-MRAM closer to practical application.

Applications

• Serves as building blocks for SOT-controlled magnetic random access memory (SOT-MRAM)
• Memory applications to provide high integration density 
• Layers of SOT-MRAM may be stacked to increase larger effective density

Advantages

• No need for any magnetic bias field
• Reduced design complexity
• More practical for wide application

State Of Development

The described SOT structure has been tested experimentally.

Patent Status