Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions

The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co25Fe75)(100-x) B-x/MgO/(Co25Fe75)(100-x)B-x (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co25Fe75)(67)B-33, while good epitaxy was observed between (001) textured MgO and (Co25Fe75)(78)B-22 electrodes. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3688039]