The dependence of critical current density of GdFeCo layer on composition of thermally assisted STT-RAM

摘要

Amorphous rare earth transitional metal (RETM) GdFeCo memory layer with RE and TM-rich compositions was fabricated in stacks of GdFeCo (10 nm)/Cu (3 nm)/[Co(0.2 nm)/Pd(0.4 nm)](6). Their magnetic properties and spin transfer torque (STT) switching of magnetization were investigated. The maximum magneto-resistance (MR) was around 0.24% for the TM-rich Gd-21.4 (Fe90Co10)(78.6) memory layer and was 0.03% for the RE-rich Gd-29.0 (Fe90Co10.)(71.0) memory layer. The critical current densities J(c) to switch the GdFeCo memory layers are in the range of 1.4 x 107 A/cm(2)-4.5 x 10(7) A/cm(2). The dependence of critical current density J(c) and effective anisotropy constant K-eff on Gd composition were also investigated. Both J(c), and Keff have maximum values in the Gd composition range from 21-29 at.%, suitable for thermally assisted STT-RAM for storage density exceeding Gb/inch(2).