Interlayer exchange coupling with Ir/(Ru, Mo, or W)/Ir composite spacers in perpendicular synthetic antiferromagnets

Abstract

We have experimentally studied the oscillatory interlayer exchange coupling (IEC) strength in synthetic antiferromagnets consisting of [Pt/Co](4)/Ir/(Ru, Mo or W)/Ir/[Co/Pt](4) with perpendicular magnetization. The Ir/(Ru, Mo or W)/Ir composite spacer enables us to obtain a substantial IEC in perpendicular synthetic antiferromagnets. The IEC with Ir/Ru/Ir spacers is as large as that with a single Ru or Ir spacer. The Ir/Mo (or W)/Ir gives rise to much larger IEC than a single Mo (or W) spacer because of the Ir insertion. Based on the results with varying the Ru (or Mo) thickness, we find that the two extremal spanning vectors of Ru (or Mo) mainly determine the oscillation periods of IEC. The Ir insertion layer affects not only the magnitude of IEC but also the peak position. With increasing the Ir thickness, the position of IEC peak moves toward a thicker spacer range. This intriguing thickness dependence of composite spacers offers a possibility to tune both the J(ex) and spacer thickness for the SAF-based spintronic applications.