Figure 1

(a) Kerr signal (A) vs. out of plane magnetic field (H _Z ) for a film stack (Sub./0.5 Ta/1 CoFeB/2 MgO/1 Ta) deposited on Si substrates with different SiOx thicknesses. The curves are shifted vertically by 1 deg for clarity. (b) The image shows a schematic illustration of the sample. The solid circles in the plot shows the Kerr rotation angle (θ _K ) as a function of the SiOx thickness. The laser wavelength (λ) is ~500 nm. The solid line represents calculation results using Eqs (5) and (6).