Reduction of spin transfer by synthetic antiferromagnets

Abstract

Synthetic antiferromagnetic layers (SAF) are incorporated into spin transfer nanopillars giving a layer composition [Cobottom/Ru/Cofixed]/Cu/Cofree, where square brackets indicate the SAF. The Cobottom and Cofixed 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 Cofree layer. Adding the Cobottom/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 Cofree layer. This may be advantageous for device applications requiring a reduction of the effects of a spin-torque, such as nanoscale current-perpendicular-to-plane magnetoresistive read heads.