Switching Characteristics of Magnetic Tunnel Junction with Amorphous CoFeSiB Free Layer

The switching characteristics of magnetic tunnel junctions (MTJs) comprising amorphous ferromagnetic CoFeSiB free layer have been investigated. CoFeSiB was used for the free layer to enhance the switching characteristics. The typical junction structure was Si/SiO2/Ta 45/Ru 9.5/IrMn 1/CoFe 7/AIO(x)/CoFeSiB (t)/Ru 60 (in nm). CoFeSiB has low saturation magnetization (M-s) of 560 emu/cm(3) and high anisotropy constant (K-u) of 2,800 erg/cm(3). These properties caused low coercivity (H) and high sensitivity in MTJs, and it also confirmed in submicrometer-sized elements by micromagnetic simulation based on the Landau-Lisfschitz-Gilbert equation. By increasing CoFeSiB free layer thickness, the switching characteristics became worse due to increase of the demagnetization field.