Interface and bulk magnetization dynamics in biaxial Fe/Cr structures induced by ultrashort optical pulses

Abstract

The interface and bulk magnetization dynamics of single-crystalline, wedge-shaped Fe(001) thin films with Cr cap layers have been studied by time-resolved magneto-optical Kerr effect (MOKE) and time-resolved magnetization-induced second harmonic generation (MSHG) using an all-optical pump-probe technique. We observed long-lived (≈1 ns) MOKE and MSHG oscillations excited by ultrashort (≈150 fs) optical pulses. They exhibit the same main resonance frequency f and damping constant. However, a 90° phase shift was observed between linear and nonlinear responses proving that MOKE and MSHG oscillations are related to the temporal variations of different magnetization components Mz and My. Additionally, we found weak oscillations at the double frequency 2f. Comparing the results of static and dynamic MSHG measurements we evaluate the in-plane amplitude of the optically excited interfacial magnetization oscillations.