Back-Hopping in Ultra-Scaled MRAM Cells

The development of advanced magnetic tunnel junctions with a footprint in the single-digit nanometer range can be achieved using an elongated multilayer ferromagnetic free layer structure. Using the spin drift-diffusion model, we investigated the back-hopping effect in ultra-scaled STTMRAM devices. Unwanted switching of the middle-layer structure has been identified as a possible cause of the back-hopping effect, which leads to a writing error in the magnetization state of the free layers. To understand the switching of the free layer, the torque acting on both parts of the composite free layer is studied in detail. A reduction in the size of MRAM components to increase the memory density leads to lower anisotropies and thus increases the likelihood of back-hopping due to the presented mechanism. A possible solution to avoid erroneous switching is to increase the magnetic anisotropy of the layers.