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Jpn. J. Appl. Phys. 44 (2005) pp. L587-L589  |Previous Article| |Next Article|  |Table of Contents|
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Letter

Dependence of Giant Tunnel Magnetoresistance of Sputtered CoFeB/MgO/CoFeB Magnetic Tunnel Junctions on MgO Barrier Thickness and Annealing Temperature

Jun Hayakawa^1,2,, Shoji Ikeda², Fumihiro Matsukura², Hiromasa Takahashi^1,2 and Hideo Ohno²

¹Hitachi, Ltd., Advanced Research Laboratory, 1-280 Higashi-koigakubo, Kokubunji-shi, 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 March 5, 2005; revised March 23, 2005; accepted March 25, 2005; published April 22, 2005)

We investigated the dependence of giant tunnel magnetoresistance (TMR) on the thickness of an MgO barrier and on the annealing temperature of sputtered CoFeB/MgO/CoFeB magnetic tunnel junctions deposited on SiO₂/Si wafers. The resistance-area product exponentially increases with MgO thickness, indicating that the quality of MgO barriers is high in the investigated thickness range of 1.15–2.4 nm. High-resolution transmission electron microscope images show that annealing at 375°C results in the formation of crystalline CoFeB/MgO/CoFeB structures, even though CoFeB electrodes are amorphous in the as-sputtered state. The TMR ratio increases with annealing temperature and is as high as 260% at room temperature and 403% at 5 K.

URL: http://jjap.jsap.jp/link?JJAP/44/L587/
DOI: 10.1143/JJAP.44.L587

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