Reduction in switching current using a low-saturation magnetization Co–Fe–(Cr, V)–B free layer in MgO-based magnetic tunnel junctions.

Magnetic properties, magnetoresistance (MR), and spin-transfer switching of magnetic tunnel junctions having a structure of Co60Fe20B20 3 nm/MgO 1 nm/(Co75Fe25)80-XCr(V)XB20 2 nm (X=0–25) were investigated. Magnetization of the (Co–Fe)–(Cr, V)–B free layer decreased from 1.2 T before substitution to 0.6 T at Cr of 10% (0.8 T at V of 10%). The MR ratio and a resistance-area product (RA) before substitution were, respectively, about 130% and about 2 Ω μm2. The MR ratio decreased to 80% at Cr of 10% and 40% at V of 10%. The RA values were almost independent of the composition. The intrinsic switching current density (Jc0) decreased from 15 to 8 MA/cm2 at Cr of 10% and 12 MA/cm2 for V of 10%. Upon the further increase in Cr and V, stable switching was difficult to observe. In summary, Jc0 decreased to half in the case of Cr, but the effect was small for V. [ABSTRACT FROM AUTHOR]