Effect of Anti-Diffusion Oxide Layer on Enhanced Thermal Stability of Magnetic Tunnel Junctions
ZHANG Zong-Zhi1, ZHAO Hui1, Cardoso S.2, Freitas P. P.2
1Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Fudan University, Shanghai 200433
2INESC-MN, R. Alves Redol, 9, 1000 and Physics Department, IST, Av. Rovisco Pais, 1096, Lisbon, Portugal
Effect of Anti-Diffusion Oxide Layer on Enhanced Thermal Stability of Magnetic Tunnel Junctions
ZHANG Zong-Zhi1;ZHAO Hui1;Cardoso S.2;Freitas P. P.2
1Department of Optical Science and Engineering, State Key Laboratory for Advanced Photonic Materials and Devices, Fudan University, Shanghai 200433
2INESC-MN, R. Alves Redol, 9, 1000 and Physics Department, IST, Av. Rovisco Pais, 1096, Lisbon, Portugal
Abstract： Magnetic tunnel junctions (MTJs) with one proper oxidized FeOx layer placed between the Al oxide barrier and the top CoFe pinned layer show large tunnelling-magnetoresistance (TMR) signals as high as 39% after anneal at 380°C. The increased TMR signal may originate from the as-deposited Fe/FeOx (non-magnetic) layers changing to Fe+magnetic FeOy layer (some Fe3O4 and mostly other kind of magnetic Fe oxide) after high temperature anneal. The maximum TMR value (TMRmax) and the corresponding temperature Ts where the TMRmax occurs upon annealing are closely associated with the oxidation time of the AlOx and FeOx layers, too long oxidation for the Fe layers is detrimental for the TMR value. In addition to the enhanced AlOx barrier quality upon anneal, the improved thermal stability is also attributed to the Mn diffusion retardation by the presence of the FeOx layer which acts as an antidiffusion layer. For MTJs without the interposed FeOx layer, the TMR signal reduction at 300°C originates from the MnIr/CoFe partially decoupling and CoFe/AlOx interface polarization loss due to the significant Mn diffusion.
2006, Vol. 23 
