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

摘要

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 ${hbox {Si--SiO}}_{2}/{hbox {Ta}}$ 45/Ru 9.5/IrMn 10/CoFe $7/{hbox {AlO}}_{x}1.5/{rm CoFeSiB}$ t (${hbox {t}}=3.5$ , 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 $3.5 {hbox {nm}}leq{hbox {t}}leq 5 {hbox {nm}}$ . When the CoFeSiB $t$ 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 $t$ 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.