MgO barrier-perpendicular magnetic tunnel junctions with CoFe/Pd multilayers and ferromagnetic insertion layers

The authors studied an effect of ferromagnetic (Co20Fe60B20 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 (T-a) of 200 degrees C and then decreased rapidly at T-a over 250 degrees 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 degrees C just after depositing bottom CoFe/Pd multilayer showed TMR ratio of 78% by postannealing at T-a= 200 degrees C. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3265740]