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Amorphous glass-coated microwires are well known by high domain wall velocities that reach up to 15 km/s. Previous works have shown that such fast domain wall dynamics can be manipulated by properly selected conditions of thermal annealing. Along with the magnetic anisotropy, the domain wall velocity is strongly influenced by surface shell of domains too. Here, the magneto-optical study of the surface reversal process in microwire is carried out by magneto-optical Kerr effect (MOKE) microscopy. It is shown that the nonplanar surface of the cylindrical samples gives rise to a complex MOKE. Trapping the domain wall in a potential, well confirmed the inclined structure of the domain wall. Such inclination can be found partially responsible for apparent high domain wall velocities measured by Sixtus-Tonks method in microwires.

The microwave permeability of flake-shaped particles is investigated using a shorted microstrip setup. Several characterizations using two distinct field configurations, with and without the presence of a static field, are performed to provide information about the magnetization dynamics of this new material. A first insight is provided through the framework of Kittel's resonance, but additional features are also found and discussed.

The propagation of a single magnetic Bloch domain wall (DW) in a mesoscopic wire is studied by use of the extraordinary Hall effect. Whereas a straight DW propagates freely in a wire with constant lateral width, the propagation in a Hall cross reveals that both DW shape and DW velocity vary strongly as a function of DW position. These results give the first experimental evidence that the dynamical properties of a magnetic DW in a patterned structure are strongly affected by the device geometry. This has to be taken into account for future applications to spin electronic devices.

Several different soft magnetic materials have been investigated by means of Magnetic Force Microscopy (MFM) using commercial Atomic Force Microscope (Nanoscope III) with slope detection. The observed contrast of basically solenoidal magnetization distributions in nanocrystalline Fe-Permalloy multilayer and single-layer Permalloy thin film elements not only reveals wall locations, and thus the subdivision of the magnetic volume into domains, but also a decomposition into subdomains hitherto undocumented. A strong influence of roughness on the magnetic fine structure is also demonstrated. Additional observations of the classical lancets of Goss texture in bulk Iron confirm the fact that the symmetries of the observed contrast are consistent with those of pendicular component of magnetization within a volume close to the sample surface. >

We can control the magnetization reversal process in Pt/Co/Pt ultra thin film devices by using mesoscopic defects fabricated by atomic force microscope (AFM) lithography. Holes and grooves locally cutting the Co layer are written by direct mechanical indentation of the metal samples by the AFM tip. The smallest lateral feature size of these artificial structures (down to 20 nm for a hole) is comparable to the intrinsic Barkhausen length (/spl sim/25 nm) of the films. The influence of the AFM fabricated structures on the magnetization reversal process in micron sized devices was studied by Kerr microscopy and extraordinary Hall effect measurements. Single point defects act as mesoscopic domain wall pinning centers, while lines effectively block the domain wall propagation. Study of the influence of well characterized defects should help understand better the magnetization reversal processes in the films.

The authors report on a materials growth study undertaken to clarify the origin of vertical Bloch lines contrast by direct optical observation in dark field on bubble garnet samples. The authors' initial guess (a large Faraday rotation) was shown to be incorrect. Rather, the influence of a low quality factor (the ratio of uniaxial energy constant to the demagnetizing energy) was detected. This agrees with a model wherein the wall tilts out of the vertical plane, at the line position. A control of lines observation is thus possible. The authors demonstrate it for specific samples grown to be put in a bias field gradient system stabilizing one single wall. >