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

摘要

The authors studied an effect of ferromagnetic (Co20Fe60B20 or Fe) layerinsertion on tunnel magnetoresistance (TMR) properties of MgO-barrier magnetictunnel junctions (MTJs) with CoFe/Pd multilayer electrodes. TMR ratio in MTJswith CoFeB/MgO/Fe stack reached 67% at an-nealing temperature (Ta) of 200degree C and then decreased rapidly at Ta over 250 degree C. The degradation ofthe TMR ratio may be related to crystallization of CoFe(B) into fcc(111) orbcc(011) texture result-ing from diffusion of B into Pd layers. MTJs which werein-situ annealed at 350oC just after depo-siting bottom CoFe/Pd multilayershowed TMR ratio of 78% by post annealing at Ta =200 degree C.