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Magnetotransport properties of CoFe/AlN/CoFe tunnel junctions with large tunnel magnetoresistance ratio

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5 Author(s)
Yoon, Tae Sick ; Research Center for Advanced Magnetic Materials, Chungnam National University, Taejon, 305-764, Korea ; Kim, Chong Oh ; Shoyama, Toshihiro ; Tsunoda, M.
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The magnetotransport properties of tunnel junctions with the structure of Ta 5 nm/Cu 20 nm/Ta 5 nm/Ni76Fe24 2 nm/Cu 5 nm/Mn75Ir25 10 nm/Co71Fe29 4 nm/AlN/Co71Fe29 4 nm/Ni76Fe2420 nm/Ta 5 nm were investigated. When the Al thickness, nitridation time, and annealing temperature were 1 nm(0.8 nm), 50 s(35 s), and 280 °C(300 °C), tunnel magnetoresistance (TMR) ratio and resistance-area product were 49%(34%) and 3×104 Ω μm2(1.5×104Ωμ m2), respectively. In order to clarify the annealing temperature dependence of TMR ratio, the local transport properties were studied using conducting atomic force microscope for Ta 5 nm/Cu 20 nm/Ta 5 nm/Ni76Fe24 2 nm/Cu 5 nm/Mn75Ir25 10 nm/Co71Fe29 4 nm/Al(0.8 nm)–N junction fabricated with the nitridation time of 35 s and Ar+N2 plasma as a function of annealing temperature. The large TMR at 300 °C, where the TMR ratio of the corresponding magnetic tunnel junction had the maximum value of 34%, could be well elucidated by the enhancement of the average barrier height ϕave, and the reduction of its fluctuation. After annealing at 340 °C, the leakage current was observed and the TMR ratio decreased.

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Applied Physics Letters  (Volume:85 ,  Issue: 1 )