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

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

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
Volume45
Issue number10
DOIs
Publication statusPublished - 2009 Oct 1

Keywords

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

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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