Co2Fe6B2/MgO-Based Perpendicular Spin-Transfer-Torque Magnetic-Tunnel-Junction Spin-Valve without [Co/Pt]n lower Synthetic-Antiferromagnetic Layer
Figures 1(a) and (b) show the spin-valve structure of a [Co/Pt]n SyAF layer with lower SyAF layer, without lower SyAF layer, respectively. The [Co/Pt]n SyAF layer without a lower SyAF layer is much thinner than that with a lower SyAF layer, as you can see in figure 1. In addition, the upper SyAF layer of p-MTJ without a lower SyAF layer is much thinner than that of p-MTJ with a lower SyAF layer because of fitting for antiferromagnetically coupling between lower and upper SyAF layer. And we studied the TMR ratio dependency on bcc nanoscale capping layer thickness of two structures by using current in-plane tunneling (CIPT) technique. In result, the maximum TMR ratios of two structures were both over 150%. In case of the p-MTJ with a [Co/Pt]n lower SyAF layer, the TMR ratio rapidly increased from 19% to 159% when the bcc nanoscale capping-layer thickness (tbcc) increased from 0.3 to 0.6 nm. Then, it abruptly decreased from 159% to 2% when tbcc decreased from 0.6 to 0.73 nm. Also, for the p-MTJ spin-valve without a [Co/Pt]n lower SyAF layer, the TMR ratio very rapidly increased from 5% to 158% when tbcc increased from 0.3 to 0.6 nm. Then, it abruptly decreased from 158% to 2% when tbcc decreased from 0.6 to 0.73 nm.
In the conference, we will present the effect of Co2Fe6B2/MgO-based perpendicular spin-transfer-torque magnetic-tunnel-junction spin-valve without [Co/Pt]n lower synthetic-antiferromagnetic layer and review the advantage of p-MTJ without lower SyAF layer. In addition, we report the physical and magnetic properties of p-MTJ by using vibrating-sampling-magnetometer (VSM), transmission-electron-microscopy (TEM). Furthermore, we review the mechanism why the magnetic properties of p-MTJs are varied by the thickness of SyAF layer.
* This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No.2014R1A2A1A01006474) and the Brain Korea 21 PLUS Program in 2014.
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