Layer-resolved magnetometry of a magnetic bilayer using the magneto-optical Kerr effect with varying angle of incidence

We determined the hysteresis loop of each layer in a magnetic bilayer of NiFe–SiO2–CoFe using the magneto-optical Kerr effect. Our method utilizes the fact that varying the angle of incidence of the optical beam changes the magnitude and sign of the polarization rotation signal contributed by each layer to the total signal. The magneto-optical signal of each layer varies differently with the angle of incidence, enabling us to determine the hysteresis loop of each. We measured the hysteresis loop of the bilayer for a range of angles of incidence, and from these loops determined the magnetization of the individual layers. We found that the magnetization of the soft NiFe layer coupled strongly to the CoFe layer for SiO2 interlayer thicknesses of <2 nm. The NiFe loop shears with decreasing interlayer thickness, increases in coercivity, and develops a two-stage switching behavior at an interlayer thickness of 1 nm.