Effect of double MgO tunneling barrier on thermal stability and TMR ratio for perpendicular MTJ spin-valve with tungsten layers

A tunneling magneto-resistance (TMR) ratio of ∼163% at an annealing temperature of 400 °C was achieved in a single MgO-based perpendicular-magnetic-tunneling-junction (p-MTJ) spin valve with a tungsten (W)/tantalum (Ta) seed and W capping layer instead of with a Ta seed and capping layer. This was done by improving the interface perpendicular magnetic anisotropy (i-PMA) characteristic of the Co2Fe6B2 free layer and face-centered-cubic (f.c.c.) crystallinity of the MgO tunneling barrier. In particular, a TMR ratio of ∼141% at an annealing temperature of 400 °C and a thermal stability at room temperature of ∼61 were achieved in a double MgO-based p-MTJ spin valve with W/Ta seed, W spacer, and W capping layers by doubling the i-PMA magnetic moment and increasing slightly magnetic anisotropy field (Hk).