Development of a system for low-temperature ultrafast optical study of three-dimensional magnon and spin orbital torque dynamics

An ultrafast vector magneto-optical Kerr effect (MOKE) microscope with integrated time-synchronized electrical pulses, two-dimensional magnetic fields, and low-temperature capabilities is reported. The broad range of capabilities of this instrument allows the comprehensive study of spin-orbital interaction-driven magnetization dynamics in a variety of novel magnetic materials or heterostructures: (1) electrical-pump and optical-probe spectroscopy allows the study of current-driven magnetization dynamics in the time domain, (2) two-dimensional magnetic fields along with the vector MOKE microscope allow the thorough study of the spin-orbital-interaction induced magnetization re-orientation in arbitrary directions, and (3) the low-temperature capability allows us to explore novel materials/devices where emergent phenomena appear at low temperature. We discuss the details and challenges of this instrument development and integration and present two datasets that demonstrate and benchmark the capabilities of this instrument: (a) a room-temperature time-domain study of current-induced magnetization dynamics in a ferromagnet/heavy metal bilayer and (b) a low-temperature quasi-static polar MOKE study of the magnetization of a novel compensated ferrimagnet.