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

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_c to switch the GdFeCo memory layers are in range of 1.6 × 10⁷ A/cm ²- 4.5 ×10⁷ A/cm ². For the Gd_21.4 (Fe₉₀Co₁₀)_78.6 memory layers, a low critical current density of 1.6×10⁷ A/cm maintaining the large thermal stability factor Δ = 210 was obtained even though the samples have a GMR structure. The J_c increased with increasing the Gd content and was found to scale with the effective anisotropy K_eff of GdFeCo layers.