Complementary multiscale magneto-optical studies based on the polar Kerr effect are carried out on an ultrathin cobalt wedge covered with a silver wedge and subsequently with the Au thick layer. A few monolayers of Ag are found to have a substantial effect on magnetic anisotropy, the coercivity field, and Kerr rotation. The silver overlayer thickness-driven magnetic reorientation from easy axis to easy plane generates a new type of 90 degrees magnetic wall for cobalt thicknesses between 1.3 and 1.8 nm. The tuning of the wall width in a wide range is possible. Tailoring of the overlayer structure can be used for ultrathin film magnetic patterning.

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The giant magnetoresistance (GMR), magnetization reversal, and domain structure of magnetron sputtered spin valve [NiFe/Au/Co/Au]N multilayers consisting of ferromagnetic layers with alternating in-plane (NiFe) and out-of-plane (Co) magnetic anisotropy has been investigated. For 0.4<tCo<1.2 nm GMR dependencies characterized by a linear and almost nonhysteretic dependence of resistance on the magnetic field were found. Within the hysteretic range of the magnetization reversal of the Co layers, for N>3, the neighboring magnetic layers were observed to be coupled. This coupling is of magnetostatic origin. The effective coupling field, estimated from GMR dependencies, is of the order of 100 kA/m. Micromagnetic simulations confirm that the domain structure of Co layers influences the behavior of NiFe layers.

We report a method of imaging of the magnetization reversal process using analysis of real-time images of magnetic domain structures in cylindrically shaped microwires. This method uses wide-field polarizing optical microscopy and is based on the magneto-optical Kerr effect (MOKE). The aperture diaphragm in MOKE microscope was used to control the incident angles of the light rays that reached the non-planar surface of the microwire and also determined the MOKE geometries. The movement of the non-central position of the hole in this diaphragm leads to a change in the orientation of the plane of incidence of the light along the perpendicular or the parallel direction to the axial direction of the wire. The visualization of the surface magnetic domain structures is obtained using polar and longitudinal MOKE geometries. The hysteresis loops were obtained by plotting the averaged image contrast as a function of the external magnetic field. The separation of the all-magnetization components is performed using different MOKE geometries in a microscope. We demonstrate the use of vector magnetometry to analyze the orientation of the magnetization in a cylindrically shaped microwire under the influence of an external magnetic field.

An elegant route for tuning the magnetic anisotropy of ultrathin Co films by Ga+ ion irradiation is presented. The magnetic anisotropy of a Pt/Co(2.6 nm)/Pt film is first changed from in-plane to out-of-plane by uniform low dose Ga+ ion irradiation at 30 keV. When increasing the dose, a second spin reorientation transition toward the sample plane is also evidenced. This could be a way to design magnetic nanowires with perpendicular anisotropy, embedded in an in-plane magnetized environment, either by irradiation through a mask or focused ion beam. Tentative explanations on the origin of these two successive spin reorientations are proposed.