Magnetization-induced nonlinear optical response of films based on nanolayers of heavy and ferromagnetic metals

Magnetization-induced effects accompanying optical second harmonic generation (SHG) in three-layer W/Co/Pt films with different thicknesses of the cobalt layer (2–10 nm) induced by longitudinal magnetic field are experimentally studied. An odd-magnetic intensity effect in the $p$ polarized second harmonic is found, with the corresponding SHG magnetic contrast increasing with the thickness of the Co layer SHGSHG. The effects are phenomenologically described by considering the bulk nonlinear polarization at the second harmonic frequency, which is proportional to the magnetization gradient in the direction normal to the structure, and the interface contribution, which is proportional to the square of the magnetization of the films.