Ultrafast laser-induced magneto-optical response of CoFeB/MgO/CoFeB magnetic tunneling junction

Understanding of ultrafast spin dynamics is crucial for future ultrafast and energy efficient magnetic memory and storage applications. We study the ultrafast laser-induced magneto-optical response of a CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ), when exciting with a short laser pulse, as a function of magnetic configuration and pump fluence. The ultrafast magnetization of the MTJ drops rapidly in the timescale of 0.33-0.37 ps, which is driven by both electron-spin scattering and spin transport mutually. Subsequently, the energy from the electron and spin reservoirs transfers into the lattice with the timescale of 1.5-2.0 and 5.0-15.0 ps through the electron-phonon and spin-phonon interactions, respectively. Our results suggest that the interfacial spin-orientation of CoFeB/MgO/CoFeB could modulate the interaction constant between spins and phonons. These findings provide insight into the role of MTJ interface in spin dynamics, which will be helpful for opto-spintronic tunnel junction stack designs and applications.