Tunneling magnetoresistance and magnetization switching of CoFeSiB free layered magnetic tunnel junctions
To reduce magnetization switching field ( Hsw) of submicrometer-sized magnetic tunnel junctions (MTJs), amorphous ferromagnetic Co 70.5Fe 4.5Si 15B 10 free layered MTJs were studied and compared to Co 75Fe 25 and Ni 80Fe 20 free layered MTJs. As a CoFeSiB film has a low saturation magnetization ( M=560 emu/cm) and a high anisotropy constant ( K=2800 erg/cm), although CoFeSiB free layered MTJs had a slightly lower tunneling magnetoresistance (TMR) ratio than that of CoFe free layered MTJ, the MTJs exhibited much lower Hsw than that of CoFe free layered MTJ, and higher sensitivity than that of CoFe and NiFe free layered MTJs. Results of micromagnetic simulation on magnetization switching processes confirmed that the magnetization in CoFeSiB free layered MTJ switched almost uniformly. Moreover, the surface roughness became more uniform and breakdown voltage increased by inserting CoFeSiB into free layer. The CoFeSiB free layered MTJ structures were found to be beneficial for the switching characteristics such as reducing Hsw and increasing the sensitivity in micrometer-sized elements.