Spin Transfer Torque Switching of Amorphous GdFeCo With Perpendicular Magnetic Anisotropy for Thermally Assisted Magnetic Memories

摘要

Giant magneto resistance (GMR) devices having amorphous GdFeCo memory layers with various Gd compositions were prepared by magnetron sputtering and subsequent micro-fabrication processes, and their spin transfer torque (STT) switching was investigated by applying a current pulse to the GMR devices. The maximum magneto-resistance (MR) was around 0.24% and the coercivity of the memory layer increased with the Gd content. The critical current densities $J_{{rm c}}$ to switch the GdFeCo memory layers are in range of $1.6 times 10^{7}$ A/cm $^{2}$– $4.5 times 10^{7}$ A/cm $^{2}$. For the Gd $_{21.4}$ (Fe $_{90}$ Co $_{10}$) $_{78.6}$ memory layers, a low critical current density of $1.6 times 10^{7}$ A/cm maintaining the large thermal stability factor $Delta = 210$ was obtained even though the samples have a GMR structure. The $J_{{rm c}}$ increased with increasing the Gd content and was found to scale with the effective anisotropy $K_{rm eff}$ of GdFeCo layers.