Reduction of spin transfer by synthetic antiferromagnets

Abstract

Synthetic antiferromagnetic layers (SAF) are incorporated into spin transfer nanopillars giving a layer composition [Co bottom /Ru/Co f ixed ]/Cu/Co f ree , where square brackets indicate the SAF. The Co bottom and Co f ixed 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 f ree 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 f ree 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.

Current-induced switching in single ferromagenetic layer nanopillar junctions

“…This ground breaking concept known as spin transfer, relies on the local interaction between a spin polarized current and the background magnetization of a ferromagnet. Spin transfer induced magnetization dynamics has been recently demonstrated experimentally in a wide variety of material systems and is rapidly reaching device maturity 3,4,5,6,7,8,9,10,11,12,13 . Furthermore, direct measurements of the magnetization dynamics 14,15,16 have shed light on the fundamental mechanism of spin transfer.…”

Relation between giant magnetoresistance and critical current for spin precession in magnetic multilayers

“…Urazhdin et al 6 and Emley et al 7 have measured ⌬R as well as I c P and I c AP on a series of samples, and some of their results are consistent with both local and nonlocal mechanisms. But the results of Urazhdin et al obtained while varying the spin-relaxation rate near one lead are consistent only with the local mechanism, suggesting that this mechanism is dominant in their samples.…”

“…On the other hand, Urazhdin et al 6 and Emley et al 7 have measured both ⌬R and I c on the same series of samples, while varying certain characteristics of layers F 1 , N, or L 2 , and found ⌬R and I c −1 to stay in a fixed ratio. One purpose of the present paper is to derive a relation of proportionality between ⌬R and I c −1 , thus providing an explanation for the experimental findings of Urazhdin et al 6 and of Emley et al 7 A second purpose is to show that the relation is valid only for one of two possible physical mechanisms responsible for current-induced torques, thus suggesting which one of the two mechanisms is dominant in these experiments.…”

Three-dimensional distribution of spin-polarized current inside(Cu∕Co)pillar structures

“…Similar effect can be realized by inserting a layer with small characteristic spin-flip resistance AR λ = λ/σ, such as Pt, Ag, Au, Ru above the last Co layer or bellow the first Co layer. Such cover layers has been used [29,30] since the first pioneering experiment [3], but their contributions to the j sp enhancement have been observed recently [30,31,32]. Figure 7 shows profiles of charge current j ch = j ↑ + j ↓ along the center axis of the (Cu/Co) 3 structure for S constant, column and constriction type structures.…”