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(2) 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 (T-a) realizing the maximum TMR ratio increased along with the TMR ratio. The MTJs with 3.0-nm-thick CoFeB deposited at 1.77W/cm(2) showed a TMR ratio of 91% at T-a 250 degrees C, where the perpendicular magnetic anisotropy is maintained. (C) 2010 The Japan Society of Applied Physics