High thermal stability of magnetic tunnel junctions with oxide diffusion barrier layers

Abstract

We developed two types of magnetic tunnel junctions (MTJs) that showed high thermal stability. One is a PtMn exchange-biased spin-valve MTJ with a CoFe/Al-oxide (AlOx)/NiFe free layer and a CoFeTaOx/CoFe pinned layer, and the other is a pseudo-spin-valve (PSV) MTJ with a CoFe/AlOx/NiFe soft layer, where AlOx and CoFeTaOx act as barriers for Ni and Mn diffusion toward the tunnel barrier, respectively. After 390 °C-1H annealing, the PSV MTJs maintained 28% and the SV MTJs 39% of tunnel magnetoresistance. Transmission electron microscopy observation of the SV MTJs after 380 °C-1H annealing revealed that the migrated Mn atoms were trapped at the CoFeTaOx layer.