High temperature annealing induced superparamagnetism in CoFeB/MgO/CoFeB tunneling junctions

Xiaoming Kou, Weigang Wang, Xin Fan, Lubna R. Shah, Rae Tao, John Q. Xiao

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We have investigated the evolution of the magnetic transport properties as a function of short annealing time in CoFeB/MgO/CoFeB based magnetic tunnel junctions (MTJs) with a free layer of 2 nm. It is found that the hysteresis behaviors in magnetoresistance (MR) loops disappear in samples annealed for 17 min. The linear region between MR and the applied field gradually increases. The MR loops without hysteresis can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

Original languageEnglish (US)
Article number083901
JournalJournal of Applied Physics
Issue number8
StatePublished - Oct 15 2010

ASJC Scopus subject areas

  • General Physics and Astronomy


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