Reduction of spin transfer by synthetic antiferromagnets

TL;DR

This paper investigates how synthetic antiferromagnetic layers (SAF) in spin transfer nanopillars can reduce spin transfer effects, potentially improving device performance by decreasing spin-torque on the free magnetic layer.

Contribution

The study demonstrates that incorporating SAF layers with antiparallel aligned Co layers reduces spin polarization and spin-torque, offering a novel approach to control spin transfer in nanopillar devices.

Findings

SAF layers decrease spin polarization of passing electrons.

Antiparallel alignment reduces dipole fields on the free layer.

Reduced spin-torque may benefit nanoscale magnetic devices.

Abstract

Synthetic antiferromagnetic layers (SAF) are incorporated into spin transfer nanopillars giving a layer composition [Co(bottom)/Ru/Co(fixed)]/Cu/Co(free), where square brackets indicate the SAF. The Co(bottom) and Co(fixed) layers are aligned antiparallel (AP) by strong indirect exchange coupling through the Ru spacer. All three magnetic layers are patterned, so this AP alignment reduces undesirable dipole fields on the Co(free) layer. Adding the Co(bottom)/Ru layers reduces the spin polarization of the electron current passing through the nanopillar, leading to a decreased spin-torque per unit current incident on the Co(free) layer. This may be advantageous for device applications requiring a reduction of the effects of a spin-torque, such as nanoscale CPP-GMR read heads.