| Popis: |
Recent developments at the authors’ lab in the study of magnetic and magneto optical (MO) properties of nanostructure arrays are reviewed. The study focus on the effect on the magnetic and MO properties that patterning has in single layer ferromagnetic thin films, and thin films made of ferromagnetic insulator heterostructures. It is demonstrated the outmost importance of the magnetostatic coupling to describe the magnetization processes of the arrays, where fields and magnetization lay in plane. In single layer patterned arrays the magnetostatic coupling is responsible of the array behaving magnetically in a collective fashion below a certain threshold interelement separation distance. As expected, shining light on a periodic structure produces reflected and diffracted spots, and the significance of MO measurements in the diffracted beams is briefly addressed. For metal/insulator/metal array structures it is again the magnetostatic coupling, and the freedom of the magnetic flux to close now in the film growth direction, the determining factor in the measured magnetization processes. This produces and antiparallel alignment of the magnetizations of top and bottom electrode at zero field when the insulating barrier is thick enough to exchange decouple the electrodes. When the tunnel junction array is fabricated in such a way that instead of having physically separated junctions the junctions share the bottom electrode, the magnetostatic coupling is still the determining factor. This happens independently of the degree of overetching of the bottom electrode below the insulating tunnel barrier, and has allowed the fabrication of 1D and 2D periodic domain patterns in continuous flat ferromagnetic films. Fabricating this kind of structures (an array on top of a continuous film) on transparent substrates allows the MO measurements at either the patterned or the flat sides of the structures. At magnetic saturation the continuous film behaves as a mirror as expected, while at selected field values, where the periodic domain structure appears, it diffracts. This is a confirmation of a pure magneto optic diffraction due to a periodic domain structure. |
