CoFeB Inserted Perpendicular Magnetic Tunnel Junctions with CoFe/Pd Multilayers for High Tunnel Magnetoresistance Ratio

The effect of Co20Fe60B20 insertion on tunnel magnetoresistance (TMR) properties of MgO barrier magnetic tunnel junctions (MTJs) was studied with Co90Fe10/Pd multilayer electrodes showing perpendicular anisotropy. The TMR ratio, which depended on the sputtering power density of the CoFeB layer, reached 43% at 1.77W/cm in MTJs with a 1.8-nm-thick CoFeB layer inserted on both sides of the MgO barrier. With increasing CoFeB layer thickness, the optimal annealing temperature (Ta) realizing the maximum TMR ratio increased along with the TMR ratio. The MTJs with 3.0-nm-thick CoFeB deposited at 1.77W/cm showed a TMR ratio of 91% at Ta 1⁄4 250 C, where the perpendicular magnetic anisotropy is maintained. # 2010 The Japan Society of Applied Physics