On/Off Ultra-Short Spin Current for Single Pulse Magnetization Reversal in a Magnetic Memory Using VO₂ Phase Transition

Ultrafast magnetization reversal of magnetic thin films induced by one single femtosecond laser light pulse, without any applied magnetic nor electrical field, known as all-optical switching has become one of the most attractive technologies for prospective ultrafast and low-energy magnetic devices. A single femtosecond laser pulse switching of a ferromagnet in specific spin valves, driven by electron pulse originating from ultrafast demagnetization of a ferrimagnetic layer, has been recently demonstrated. This opens the way to ultrafast and energy-efficient writing for magnetic memory. Here, a new functionality is presented through introducing a thin VO₂ into the specific spin valve, where a switchable ultra-short polarized electron pulse by thermally triggering the phase transition of VO₂ to dynamically control the switching of the ferromagnet is experimentally achieved. It is demonstrated that the generated ultra-short electron pulse can be free to pass through the VO₂ in its metallic state while it is blocked in its insulating state. Additionally, the change on electrical and optical properties of VO₂ during the phase transition leads to various possible magnetic states. On/off ultra-short spin current controlled by phase transition paves the way to address specific ultra-fast spintronic devices in large array devices.