Improved thermal stability of ferromagnetic tunnel junctions with a CoFe/CoFeO/sub x//CoFe pinned layer

Annealing temperature dependence of the tunnel magnetoresistance (TMR) ratio for magnetic tunnel junctions with CoFeO/sub x/ inserted in the pinned layer was investigated. A junction with a CoFe/CoFeO/sub x//CoFe pinned layer exhibited TMR ratios of 46.5% and 42.5% after annealing at 350(degree)C and 375(degree)C, respectively. The reason for the improvement of the thermal stability is related to oxygen diffusion from the CoFeO/sub x/ layer, and there is a possibility that CoFeO/sub x/ plays the role of a Mn (in MnIr exchange layer) diffusion barrier.