Magneto-Transport Characteristics of Magnetic Tunnel Junction With a Synthetic Antiferromagnetic Amorphous CoFeSiB Free Layer

A synthetic antiferromagnet (SAF) structure comprising two ferromagnetic amorphous CoFeSiB layers was employed as a free layer in magnetic tunnel junctions (MTJs) to enhance magnetotransport and magnetization switching performance. In Si-SiO₂/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlO_<i>x</i>1.5/CoFeSiB t (t=3.5 , 4.0, 4.5, 5.0)/Ru 1.0/CoFeSiB 7-t/Ru 60 (nm) MTJ structures, the tunneling magnetoresistance (TMR) ratio, interlayer coupling field, and switching field all showed layer thickness dependence for 3.5&nbsp;nm les t les 5&nbsp;nm . When the CoFeSiB <i>t</i> layer (a lower ferromagnetic layer in the SAF structure) became thinner, a lower TMR ratio with a lower switching field was observed. Whereas, when the CoFeSiB <i>t</i> layer became thicker, a higher junction resistance with a lower interlayer coupling field was observed. This was resulted from the decrement of saturation magnetization and the smooth tunnel barrier/free-layer interface formation, respectively.