Field-free Magnetization Switching by Utilizing the Spin Hall Effect and Interlayer Exchange Coupling of Iridium

TL;DR

This paper demonstrates a method for field-free magnetization switching in perpendicular MRAM using an Iridium layer that provides spin Hall effect-induced SOTs and induces interlayer exchange coupling, eliminating the need for external magnetic fields.

Contribution

The study introduces a novel Iridium layer that enables field-free SOT-driven magnetization switching by combining spin Hall effect and interlayer exchange coupling.

Findings

Successful field-free magnetization switching demonstrated experimentally.

Switching characterized by domain nucleation and expansion.

Micromagnetic modeling provides insight into the reversal process.

Abstract

Magnetization switching by spin-orbit torque (SOT) via spin Hall effect represents as a competitive alternative to that by spin-transfer torque (STT) used for magnetoresistive random access memory (MRAM), as it does not require high-density current to go through the tunnel junction. For perpendicular MRAM, however, SOT driven switching of the free layer requires an external in-plane field, which poses limitation for viability in practical applications. Here we demonstrate field-free magnetization switching of a perpendicular magnet by utilizing an Iridium (Ir) layer. The Ir layer not only provides SOTs via spin Hall effect, but also induce interlayer exchange coupling with an in-plane magnetic layer that eliminates the need for the external field. Such dual functions of the Ir layer allows future build-up of magnetoresistive stacks for memory and logic applications. Experimental observations show that the SOT driven field-free magnetization reversal is characterized as domain nucleation and expansion. Micromagnetic modeling is carried out to provide in-depth understanding of the perpendicular magnetization reversal process in the presence of an in-plane exchange coupling field.