Magnetoresistance and switching properties of magnetic tunnel junctions using amorphous CoSiB free layer

We have investigated the tunneling magnetoresistance ( TMR) effect and switching characteristics for magnetic tunnel junctions ( MTJs) with amorphous ferromagnetic Co75Si15B10 free layer compared to MTJs with Co75Fe25, Ni80Fe20 and Co70.5Fe4.5Si15B10 free layers. Since amorphous CoSiB had a low saturation magnetization ( M-s = 470 emu/ cm(3)) and a modest anisotropy constant ( K-u = 1500 erg/ cm(3)), the MTJ with this free layer showed better switching characteristics, especially CoSiB- based MTJ exhibited much lower switching field ( H-sw = 3 Oe) and interlayer coupling field ( H-int = 10 Oe) than MTJs with the other free layers, but TMR ratio showed relatively low value ( 23%). In addition, the bias voltage dependence of TMR ratio in CoSiB- based double MTJ was improved compared to that of single MTJ. It was expected that CoSiB was a potential candidate material as the free layer for use in high- density magnetic random access memory ( MRAM) with an MTJ element. (c) 2006 Elsevier B. V. All rights reserved.