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 M z and M y . Additionally, we found weak oscillations at the double frequency 2 f . Comparing the results of static and dynamic MSHG measurements we evaluate the in-plane amplitude of the optically excited interfacial magnetization oscillations.