Integrating magnetic tunnel junctions with femtosecond laser pulses

Spintronic MRAM is highly promising towards a next-generation “universal” memory paradigm. As its key building block, perpendicular magnetic tunnel junctions (p-MTJs) have been an active field of research, aiming at a high access speed with low power consumption. However, state-of-the-art p-MTJs are still fundamentally limited by the spin precession process, resulting in a sub-ns speed limitation. Recently, manipulating or even switching the magnetization of ferrimagnets in a highly non-equilibrium regime has been realized by a single femtosecond (fs) laser pulse, leading to a plethora of opportunities for device applications. In this presentation, we report our recent experimental progress on integrating p-MTJ with fs lasers. First, we introduce fs laser-assisted switching in a high-performance p-MTJ device using a direct electrical readout. Reconfigurable switching operations and a switching phase diagram are shown by the interplay of the laser and synchronized field. Second, we demonstrate fs laser-induced all-optical switching of a p-MTJ, by using a composite free layer structure employing interlayer RKKY coupling. All-optical switching speed within 10 ps is demonstrated, with a high energy efficiency and a decent TMR ratio. We believe our hybrid research approach might pave the way towards a new category of integrated photonic memory, as well as an alternating scheme for next-generation MRAM design.