Probe and Control of Photo-excited Magnetization Precession in Co/Pd Multilayer Films

Understanding the fundamental limits for ultrafast manipulation of magnetism in ordered spin systems is vital for the development of novel spin-based devices as well as very-efficient magneto-optical recording. In this talk, we present the dynamics of photo-excited precession of magnetization (PEPM) in Co/Pd multilayer films using time resolved magneto-optical Kerr effect (TRMOKE) for different pump fluences. Several Co/PD layers with the Co thicknesses ranging from 0.2 nm to 0.74 nm were measured in magnetic fields from 0 mT to 250 mT. PEPM relies on the effective field which is composed of the anisotropic field, demagnetization field, and the external field. We report on studies where we vary the excitation intensity, to probe the region in which rapid changes in the demagnetization field are the dominant effect for PEPM and the region of lower fluencies (< 10 mJ/cm²) where the anisotropic magnetic field in the multilayer thin film samples becomes the dominant effect for PEPM. These low fluencies allow us to better probe the effect of the in-plane and out of plane magnetic anisotropy on the amplitude of oscillation of PEPM.