Hybrid memory layer with low Curie temperature CoPd/Pd multilayer for high-density magnetic random access memory cells.

摘要

We investigated switching behavior of the hybrid structures consisting of low Curie temperature (T_C ) and high T_C layers. The T_C of [Co (0.3 nm)/Pd (1.2 nm)]₆ and [Co₅₄Pd₄₆ (0.3 nm)/Pd (1.2 nm)]₆ multilayers (MLs) were confirmed to have much higher than 200 °C and around 110 °C, respectively. In the bi-ML hybrid structure with Co/Pd and CoPd/Pd MLs, the two MLs are exchange-coupled at room temperature, and the CoPd/Pd ML was switched following the magnetization of the high T Co/Pd ML at high temperature (~170 °C) at which the CoPd/Pd ML becomes paramagnetic. The tri-layered hybrid structure with a stack of [Co (0.4 nm)/Pt (1.2 nm)]₆/[Co₄₈Pd₅₂ (0.3 nm)/Pd (1.2 nm)]₃/[Co (0.4 nm)/Pd (1.2 nm)]₃ was also investigated. The tri-ML stack showed one-step hysteresis loop at room temperature and two-step loop at higher than 120 °C due to the loss of magnetic order of the intermediate low T_C CoPd/Pd ML. From the data of tri-ML stack, the exchange coupled and decoupled situations between Co/Pt and Co/Pd MLs were found to be realized by changing the temperature from room temperature to around 150 °C.