Micro fabrication and magnetoelectric properties of amorphous magnetic-tunnel-junctions with Co-Fe-B/Al-O/Co-Fe-B hardcore structure

Both single-barrier magnetic tunnel junctions (SBMTJs) and double-barrier magnetic tunnel junctions (DBMTJs) with an amorphous hardcore structure of Co60Fe20B20/Al-O/Co60Fe20B20 were microfabricated. A high TMR ratio of 102.2% at 4.2 K was observed in the SBMTJs after annealing at 265 degrees C for 1 h. High TMR ratio of 56.2%, low junction resistance-area product RS of 4.6 k Omega mu m(2), small coercivity H-C = 25 Oe, and relatively large bias-voltage-at-half-maximum TMR with the value V-1/2 greater than 500 mV at room temperature (RT) had been achieved in such Co-Fe-B SBMTJs. Whereas, high TMR ratio of 60% at RT and 89% at 30 K, low junction resistance-area product RS of 7.8 k Omega mu m(2) at RT and 8.3 k Omega mu m(2) at 30 K, low coercivity H-C = 8.5 Oe at RT and H-C = 14 Oe at 30 K, and relatively large bias-voltage-at-half-maximum TMR with the value V-1/2 greater than 1150 mV at RT had been achieved in the Co-Fe-B DBMTJs. Temperature dependence of the TMR ratio, resistance, and coercivity from 4.2 K to RT, and applied voltage dependence of the TMR ratio and resistance at RT for such amorphous MTJs were also investigated. (C) 2006 Elsevier B.V. All rights reserved.