Abstract
Buffer layer dependence of tunnel magnetoresistance (TMR) effects was investigated in Co2Fe0.4Mn0.6Si (CFMS)/MgO/Co50Fe50 magnetic tunnel junctions (MTJs). Pd, Ru and Cr were selected for the buffer layer materials, and MTJs with three different CFMS thicknesses (30, 5, and 0.8 nm) were fabricated. A maximum TMR ratio of 136% was observed in the Ru buffer layer sample with a 30-nm-thick CFMS layer. TMR ratios drastically degraded for the CFMS thickness of 0.8 nm, and the values were 26% for Cr buffer layer and less than 1% for Pd and Ru buffer layers. From the annealing temperature dependence of the TMR ratios, amounts of interdiffusion and effects from the lattice mismatch were discussed.
Highlights
Spin transfer torque magnetoresistive random access memory (STT-MRAM) has attracted much attention as a next-generation non-volatile memory
The chemical composition ratio and buffer layer dependence of perpendicular magnetic anisotropy (PMA) was investigated systematically in our previous work,[24,25,26] in which it was reported that the thickness of magnetic dead layer of Co2(Fe-Mn)Si depends on the buffer layer materials and annealing temperatures, and this was considered to originate from the differences in lattice mismatch and interdiffusion between the buffer layer material and the Co2(Fe-Mn)Si layer
For the Pd buffer layer, the tunnel magnetoresistance (TMR) ratio shows the largest value of 119% for tCFMS = 30 nm and T anneal = 400 ◦C
Summary
Tunnel magnetoresistance of 604% at by suppression of Ta diffusion in pseudo-spin-valves annealed at high temperature.
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