We investigated the relationship between tunnel magnetoresistance (TMR) ratio and the crystallization of CoFeB layers through annealing in magnetic tunnel junctions (MTJs) with MgO barriers that had CoFe/Ru/CoFeB synthetic ferrimagnet pinned layers with varying Ru spacer thickness (tRu). The TMR ratio increased with increasing annealing temperature (Ta) and tRu, reaching 361% at Ta=425°C, whereas the TMR ratio of the MTJs with pinned layers without Ru spacers decreased at Ta over 325°C. Ruthenium spacers play an important role in forming a (001)-oriented bcc CoFeB pinned layer, resulting in a high TMR ratio through annealing at high temperatures.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)