86% TMR at 4.2 K for amorphous magnetic-tunnel-junctions with Co60Fe20B20 as free and pinned layers

Single barrier magnetic-tunnel-junctions (MTJs) with the layer structure of Ta(5)/Cu(30)/Ta(5)/Ni79Fe21(5)/Ir-22 Mn-78(12)/Co60Fe20B20(4)/Al(0.8)-oxide/Co60Fe20B20(4)/Cu(30)/Ta(5) [thickness unit: nm] using the amorphous Co60Fe20B20 alloy as free and pinned layers were micro-fabricated. The experimental investigations showed that the tunnel magnetoresistance (TMR) ratio and the resistance decrease with increasing dc bias voltage from 0 to 500 mV or with increasing temperature from 4.2 K to RT. A high TMR ratio of 86.2% at 4.2 K, which corresponds to the high spin polarization Of Co60Fe20B20, 55%, was observed in the MTJs after annealing at 270 degrees C for 1 h. High TMR ratio of 53.1%, low junction resistance-area product RS of 3.56 k Omega/mu m(2), small coercivity H-C of <= 4 Oe, and relatively large bias-voltage-at-half-maximum TMR with the value V-1/2 of greater than 570 mV at RT have been achieved in such Co-Fe-B MTJs.