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

Abstract

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.