Exploring integrated Spin-Orbit Torque SOT-MRAM for nonvolatile, low power, and ultrafast magnetic memories

There is considerable interest in electrically controlling nano-magnets in order to develop non-volatile magnetic memories (MRAM) [1]. Most advanced MRAM devices are magnetic tunnel junctions (MTJ) that consist of two ferromagnetic layers separated by a very thin oxide barrier, one of the layer being the storage layer, the other is used as reference layer. Depending on the relative orientation of the magnetization of these two layers (parallel/ anti-parallel), the MTJ cell will exhibit low/high resistance through the tunnel magneto-resistance effect (TMR), defining the reading state (0/1). The writing operation relies on either the Spin Transfer Torque (STT)[1] or the Spin-Orbit Torque (SOT)[2,3]. The SOT mechanism allows for decoupling the read and write operations using a novel 3-terminal geometry. The focus of this PhD will address the two main challenges of SOT-MRAM: field-free switching and reduced power consumption. [1] C. Chappert et al., Nature Material (2007), [2] M. Miron et al., Nature (2011), A. Manchon et. al, arxiv 1801.09636; [3] K. Garello et al., Nature Nanotech (2013).