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[Display omitted] • Optical writing and electrical reading of magnetic states within nanoscale ferromagnetic tunnel junctions. • Downscaling of the perpendicularly magnetized nanodevices while retaining the desired functionalities. • Correlation between the switching probability, magnetic anisotropy, and the diameter of the nanodevices. • Probing the depth-resolved hysteresis and time-resolved magnetization dynamics in a full stack magnetic tunnel junction film. Magnetic tunnel junctions (MTJs) are elementary units of magnetic memory devices. For high-speed and low-power data storage and processing applications, fast reversal of the magnetization by an ultrashort laser pulse is extremely important. We demonstrate single-shot switching of Tb/Co-multilayer based nanoscale MTJs by combining the optical writing and the electrical read-out methods. A 90-fs-long laser pulse switches the magnetization of the storage layer (SL). The change in the tunneling magnetoresistance (TMR) between the SL and a reference layer (RL) is probed electrically across the oxide barrier. Single-shot switching is demonstrated by varying the cell diameter from 300 nm to 20 nm. The anisotropy, magnetostatic coupling, and switching probability exhibit cell-size dependence. By suitable association of laser fluence and magnetic field, successive commutation between high-resistance and low-resistance states is achieved. The nature of the magnetization reversal of both SL and RL in a continuous film is probed with a depth-resolved magneto-optical Kerr effect (MOKE) magnetometry. The ultrafast dynamics in the continuous full-MTJ stack is investigated with the time-resolved pump–probe technique. Our experimental findings provide strong support for the growing interest in ultrafast spintronic devices. [ABSTRACT FROM AUTHOR]

• Broad overview on eight major methods for spin generation is given with their physical principles. • Corresponding device applications are discussed based on their recent development. • Future perspectives on the spintronic devices are provided at the end of this review. Spintronics is one of the emerging fields for the next-generation nanoelectronic devices to reduce their power consumption and to increase their memory and processing capabilities. Such devices utilise the spin degree of freedom of electrons and/or holes, which can also interact with their orbital moments. In these devices, the spin polarisation is controlled either by magnetic layers used as spin-polarisers or analysers or via spin–orbit coupling. Spin waves can also be used to carry spin current. In this review, the fundamental physics of these phenomena is described first with respect to the spin generation methods as detailed in Sections 2 ~ 9. The recent development in their device applications then follows in Sections 10 and 11. Future perspectives are provided at the end. [ABSTRACT FROM AUTHOR]