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

Abstract

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[Formula: see text] (Fe[Formula: see text]Co[Formula: see text])[Formula: see text] memory layer and was −0.03% for the RE-rich Gd[Formula: see text] (Fe[Formula: see text]Co[Formula: see text])[Formula: see text] memory layer. The critical current densities [Formula: see text] to switch the GdFeCo memory layers are in the range of [Formula: see text] A/cm2–[Formula: see text] A/cm2. The dependence of critical current density [Formula: see text] and effective anisotropy constant [Formula: see text] on Gd composition were also investigated. Both [Formula: see text] and [Formula: see text] have maximum values in the Gd composition range from 21–29 at.%, suitable for thermally assisted STT-RAM for storage density exceeding Gb/inch2.