Significant reduction of coercivity without reduction of tunneling magnetoresistance ratio of CoFeB∕MgO∕CoFeB-based magnetic tunnel junction using sandwich-structured free layer

Abstract

We report the significant reduction of coercivity (Hc) without huge drop of tunneling magnetoresistance ratio (TMR) in the CoFeB∕MgO∕CoFeB-based magnetic tunnel junction by employing sandwich-structured free layer of CoFeB/metallic spacer/NiFe. Strong magnetostatic coupling without physical contact induces magnetic softness from NiFe to CoFeB and avoids considerable reduction of TMR. This achievement satisfies the requirements given to the magnetic read head in hard disk drive and the spin torque transfer magnetic random access memory for the application to the higher areal density and the reduction of critical current density for current-induced magnetization switching, respectively.