Magnetization switching and tunneling magnetoresistance effects of synthetic antiferromagnet free layers consisting of amorphous NiFeSiB

Abstract

A synthetic antiferromagnet (SAF) structure comprising of ferromagnetic amorphous Ni16Fe62Si8B14 layers has been devised and employed as a free layer of magnetic tunnel junctions (MTJs) to enhance cell switching performance. We observed -0.03 erg/cm(2) of exchange coupling energy (J(ex)) by inserting a 0.5 nm Ru layer in between NiFeSiB layers. In Si/SiO2/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO(x)1.5/(single NiFeSiB 7) or [NiFeSiB(t)/Ru 0.5/NiFeSiB(7-t)]/Ru 60(nm) MTJ structures, we found size dependence of the switching field originating from the lower J(ex) both experimentally and by simulation. The NiFeSiB SAF structure showed lower switching field than traditional CoFe and CoFeB SAF structures. This is because NiFeSiB possesses low saturation magnetization (M-s=800 emu/cm(3)) and high anisotropy constant (K-u=2,700 erg/cm(3)). These properties were proven beneficial for the switching characteristics such as reducing the coercivity (H-c) and increasing the sensitivity in micrometer to submicrometer sized elements. (c) 2005 American Institute of Physics.