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

doi:10.1109/TMAG.2009.2023237

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 journal › Article › peer-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 (T_a 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 T_a = 473 K and monotonically decreased at T_a over 523 K. The TMR ratio with Co₅₀Fe₅₀ insertion increased up to 3% at T_a = 573 K and then decreased to 0.4% at T_a = 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 T_a 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 language	English
Article number	5257164
Pages (from-to)	3476-3479
Number of pages	4
Journal	IEEE Transactions on Magnetics
Volume	45
Issue number	10
DOIs	https://doi.org/10.1109/TMAG.2009.2023237
Publication status	Published - 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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Perpendicular magnetic tunnel junctions with CoFe/Pd multilayer electrodes and an MgO barrier. / Park, Ji Ho; Ikeda, Shoji; Yamamoto, Hiroyuki; Gan, Huadong; Mizunuma, Kotaro; Miura, Katsuya; Hasegawa, Haruhiro; Hayakawa, Jun; Ito, Kenchi; Matsukura, Fumihiro ; Ohno, Hideo.

In: IEEE Transactions on Magnetics, Vol. 45, No. 10, 5257164, 01.10.2009, p. 3476-3479.

Research output: Contribution to journal › Article › peer-review

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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.",

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AU - Ikeda, Shoji

AU - Yamamoto, Hiroyuki

AU - Gan, Huadong

AU - Mizunuma, Kotaro

AU - Miura, Katsuya

AU - Hasegawa, Haruhiro

AU - Hayakawa, Jun

AU - Ito, Kenchi

AU - Matsukura, Fumihiro

AU - Ohno, Hideo

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N2 - 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.

AB - 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.

KW - CoFe/Pd multilayer electrodes

KW - MgO barrier

KW - Perpendicular magnetic anisotropy

KW - Tunnel magnetoresistance (TMR)

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