Temperature Dependence of Critical Current Density of Spin Transfer Torque Switching Amorphous GdFeCo for Thermally Assisted MRAM

Amorphous GdFeCo with various Gd compositions used as memory layers in giant magneto-resistance (GMR) devices were prepared by magnetron sputtering and subsequent micro-fabrication processes, and their magnetic properties and spin transfer torque (STT) switching of magnetization were investigated. The magneto-resistance (MR) of the GMR device with the Gd₂₃(Fe₉₀Co₁₀)₇₇ memory layer decreased with elevating temperature. The effective anisotropy constant K_eff also decreased with temperature. It is noted that the critical current density J_c for the STT switching reduced about 10% in spite of a slight temperature increase of 10 °C which was confirmed from the temperature dependence of J_c of the GMR device with Gd₂₂(Fe₉₀Co₁₀)₇₈ memory layer. The K_eff reductions were considered to contribute to the decrease of J_c. From these data, it is expected that J_c would be drastically reduced with increasing temperature for the devices with the GdFeCo memory layers exhibiting sufficiently large thermal stability at room temperature.