Perpendicular magnetic tunnel junctions with CoFe/Pd multilayer electrodes and an MgO barrier

Ji Ho Park, Shoji Ikeda, Hiroyuki Yamamoto, Huadong Gan, Kotaro Mizunuma, Katsuya Miura, Haruhiro Hasegawa, Jun Hayakawa, Kenchi Ito, Fumihiro Matsukura, Hideo Ohno

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We studied the magnetic and magnetoresistance characteristics of pseudospin-valve magnetic tunnel junctions (MTJs) based on CoFe/Pd multilayer electrodes with perpendicular magnetic anisotropy and an MgO barrier. The MTJs at annealing temperature (Ta of 473 K showed a tunnel- magnetoresistance (TMR) ratio of 1.5%. An fee (lll)-oriented texture of the bottom and top Co90Fe10/Pd multilayer electrodes, together with an imperfectly crystallized MgO, were revealed by cross-sectional TEM images. The TMR properties of perpendicular MTJs with aCo20Fe 60B20Co50fe50 or layer inserted between the CoFe/Pd multilayer electrodes and the MgO barrier were also studied. The TMR ratio with Co20Fe60B20 insertion was 1.7% at Ta = 473 K and monotonically decreased at Ta over 523 K. The TMR ratio with Co50Fe50 insertion increased up to 3% at Ta = 573 K and then decreased to 0.4% at Ta = 598 K. The influence of the Pd layer on CoFeB was studied by using the simplified structures of Pd/CoFeB/MgO/CoFeB/Pd and Ta/CoFeB/MgO/CoFeB/Ta with inplane anisotropy. A former structure with Pd resulted in reduced TMR ratio which decreases with increasing Ta whereas MTJs with a Ta-based structure showed a monotonic increase of a TMR ratio. The low TMR ratio observed in Pd-containing structures appears to result from crystallization of CoFeB in an unfavorable crystal orientation.

Original languageEnglish
Article number5257164
Pages (from-to)3476-3479
Number of pages4
JournalIEEE Transactions on Magnetics
Issue number10
Publication statusPublished - 2009 Oct


  • CoFe/Pd multilayer electrodes
  • MgO barrier
  • Perpendicular magnetic anisotropy
  • Tunnel magnetoresistance (TMR)


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