The authors studied an effect of ferromagnetic (Co20 Fe 60 B20 or Fe) layer insertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetic tunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJs with CoFeB/MgO/Fe stack reached 67% at annealing temperature (Ta) of 200 °C and then decreased rapidly at Ta over 250 °C. The degradation of the TMR ratio may be related to crystallization of CoFe(B) into fcc(111) or bcc(011) texture resulting from diffusion of B into Pd layers. MTJs which were in situ annealed at 350 °C just after depositing bottom CoFe/Pd multilayer showed TMR ratio of 78% by postannealing at Ta =200 °C.
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