Magnetic configuration at ferromagnet-semiconductor interfaces: static and dynamic studies

This doctoral research delves into the captivating realm of metal/semiconductor heterostructures, with a focus on investigating the manipulation and transport of electron spin in solid-state systems for potential application in Spintronics. At the heart of our study lies a Ni/Si heterostructure, which is explored through ultrafast demagnetization, unveiling the dynamics of spin-polarized superdiffusive currents. The development of a Ni/Si heterostructure began with the generation of a laser-induced spin-polarized superdiffusive current, with the system's construction necessitating the creation of an EUV polarimeter for detecting the reflected beam polarization. The thesis investigates magnetodynamics at both the Ni M2,3 and Si L2,3 absorption edges, revealing an effective spin current propagation velocity of 0.2 nm/fs, supporting theoretical predictions. A significant observation was the presence of an equilibrium magnetization state in the proximal silicon layer of the Ni/Si heterostructure, which was unanticipated due to silicon's weakly diamagnetic nature. A systematic analysis, using samples with varying semiconductor dopings and applying the static XMCD technique, demonstrated a complex interplay at the interface. The implications of this study are momentous for Spintronics, particularly because of the verified magnetic coupling between the ferromagnetic layer and the underlying semiconductor. The results presented represent an important step in advancing silicon-based spintronic systems and paves the way for the design of energy-efficient and faster electronic devices leveraging the spin degree of an electron.