TY - JOUR
T1 - Current-induced magnetization switching in MgO barrier magnetic tunnel junctions with CoFeB-based synthetic ferrimagnetic free layers
AU - Hayakawa, Jun
AU - Ikeda, Shoji
AU - Miura, Katsuya
AU - Yamanouchi, Michihiko
AU - Lee, Young Min
AU - Sasaki, Ryutaro
AU - Ichimura, Masahiko
AU - Ito, Kenchi
AU - Kawahara, Takayuki
AU - Takemura, Riichiro
AU - Meguro, Toshiyasu
AU - Matsukura, Fumihiro
AU - Takahashi, Hiromasa
AU - Matsuoka, Hideyuki
AU - Ohno, Hideo
N1 - Funding Information:
The authors would like to thank Dr. Y. Ohno and Dr. T. Tanikawa for valuable help with the experiment and discussion. This work was supported in part by “High-Performance Low-Power Consumption Spin Devices and Storage Systems” program under Research and Development for Next-Generation Information Technology of MEXT.
PY - 2008/7
Y1 - 2008/7
N2 - We investigated the effect of using a synthetic ferrimagnetic (SyF) free layer in MgO-based magnetic tunnel junctions (MTJs) on current-induced magnetization switching (CIMS), particularly for application to spin-transfer torque random access memory (SPRAM). The employed SyF free layer had a Co 40Fe40B20/Ru/Co40Fe 40B20 and Co20Fe60B 20/Ru/Co20Fe60B20 structures, and the MTJs (100 × (150-300) nm2) were annealed at 300°C. The use of SyF free layer resulted in low intrinsic critical current density (J c0) without degrading the thermal-stability factor (E/kBT, where E, kB, and T are the energy potential, the Boltzmann constant, and temperature, respectively). When the two CoFeB layers of a strongly antiferromagnetically coupled SyF free layer had the same thickness, J c0 was reduced to 2-4 × 106 A/cm2. This low Jc0 may be due to the decreased effective volume under the large spin accumulation at the CoFeB/Ru. The E/kBT was over 60, resulting in a retention time of over ten years and suppression of the write current dispersion for SPRAM. The use of the SyF free layer also resulted in a bistable (parallel/antiparallel) magnetization configuration at zero field, enabling the realization of CIMS without the need to apply external fields to compensate for the offset field.
AB - We investigated the effect of using a synthetic ferrimagnetic (SyF) free layer in MgO-based magnetic tunnel junctions (MTJs) on current-induced magnetization switching (CIMS), particularly for application to spin-transfer torque random access memory (SPRAM). The employed SyF free layer had a Co 40Fe40B20/Ru/Co40Fe 40B20 and Co20Fe60B 20/Ru/Co20Fe60B20 structures, and the MTJs (100 × (150-300) nm2) were annealed at 300°C. The use of SyF free layer resulted in low intrinsic critical current density (J c0) without degrading the thermal-stability factor (E/kBT, where E, kB, and T are the energy potential, the Boltzmann constant, and temperature, respectively). When the two CoFeB layers of a strongly antiferromagnetically coupled SyF free layer had the same thickness, J c0 was reduced to 2-4 × 106 A/cm2. This low Jc0 may be due to the decreased effective volume under the large spin accumulation at the CoFeB/Ru. The E/kBT was over 60, resulting in a retention time of over ten years and suppression of the write current dispersion for SPRAM. The use of the SyF free layer also resulted in a bistable (parallel/antiparallel) magnetization configuration at zero field, enabling the realization of CIMS without the need to apply external fields to compensate for the offset field.
KW - CoFeB
KW - Current-induced magnetization switching
KW - MgO barrier
KW - Synthetic ferrimagnetic free layer
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U2 - 10.1109/TMAG.2008.924545
DO - 10.1109/TMAG.2008.924545
M3 - Article
AN - SCOPUS:45849144387
SN - 0018-9464
VL - 44
SP - 1962
EP - 1967
JO - IEEE Transactions on Magnetics
JF - IEEE Transactions on Magnetics
IS - 7
M1 - 4544915
ER -