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Jpn. J. Appl. Phys. 45 (2006) pp. L1057-L1060  |Next Article|  |Table of Contents|
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Current-Induced Magnetization Switching in MgO Barrier Based Magnetic Tunnel Junctions with CoFeB/Ru/CoFeB Synthetic Ferrimagnetic Free Layer

Jun Hayakawa^1,2, Shoji Ikeda², Young Min Lee², Ryutaro Sasaki², Toshiyasu Meguro², Fumihiro Matsukura², Hiromasa Takahashi^1,2 and Hideo Ohno²

¹Advanced Research Laboratory, Hitachi, Ltd., 1-280 Higashi-koigakubo, Kokubunji, Tokyo 185-8601, Japan
²Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan

(Received September 13, 2006; accepted September 21, 2006; published online October 6, 2006)

We report the intrinsic critical current density (J_c0) in current-induced magnetization switching and the thermal stability factor (E/k_BT, where E, k_B, and T are the energy potential, the Boltzmann constant, and temperature, respectively) in MgO based magnetic tunnel junctions with a Co₄₀Fe₄₀B₂₀(2 nm)/Ru(0.7–2.4 nm)/Co₄₀Fe₄₀B₂₀(2 nm) synthetic ferrimagnetic (SyF) free layer. We show that J_c0 and E/k_BT can be determined by analyzing the average critical current density as a function of coercivity using the Slonczewski's model taking into account thermal fluctuation. We find that high antiferromagnetic coupling between the two CoFeB layers in a SyF free layer results in reduced J_c0 without reducing high E/k_BT.

URL: http://jjap.jsap.jp/link?JJAP/45/L1057/
DOI: 10.1143/JJAP.45.L1057

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