We present direct imaging of magnetic flux structures in the anisotropic, spin-triplet superconductor Sr 2 RuO 4 using a scanning µSQUID microscope. Individual quantized vortices were seen at low magnetic fields. Coalescing vortices forming flux domains were revealed at intermediate fields.Based on our observations we suggest that a mechanism intrinsic to the material stabilizes the flux domains against the repulsive vortex-vortex interaction. Topological defects like domain walls can provide this, implying proof for unconventional chiral superconductivity.

of the spin injection. To avoid these two phenomena we investigate the growth of Mn 5 Ge 3 and C-doped Mn 5 Ge 3 films on Ge(111) substrates by molecular beam epitaxy at room-temperature. The reactive deposition epitaxy method is used to deposit these films. Reflection high energy electron diffraction, X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy indicate that the crystalline quality is very high. Magnetic characterizations by superconducting quantum interference device and ferromagnetic resonance reinforce the structural analysis results on the thin films quality.

Magnetic flux structures in single crystals of the layered spin triplet superconductor Sr 2 RuO 4 are studied by scanning micro SQUID Force microscopy. Vortex chains appear as the applied field is tilted along the in-plane direction of the superconductor. The vortex chains align along the direction of the in-plane component of the applied magnetic field. The decoration of inplane vortices by crossing Abrikosov vortices is observed: two vortex orientations are apparent simultaneously, one along the layers and the other perpendicular to the layers. The crossing vortices appear preferentially on the in-plane vortices.

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The optical absorption in flash‐evaporated 2O3 thin films is studied in the photon energy range 0.6 to 6.2 eV. Tetragonal Bi2O3 is found to be an indirect gap insulator with an energy gap of ≈ 2.6 eV at room temperature. At 5.6 eV a peak in the extinction is evidenced. In the transparent region of the layers the variations in transmission are mainly due to interference phenomena. Optical constants and thickness are determined from the fringe pattern of the transmission spectrum.

RésuméInteractions between pairs of magnetic domain walls (DW) and pinning by radial constrictions were studied in cylindrical nanowires with surface roughness. It was found that a radial constriction creates a symmetric pinning potential well, with a change of slope when the DW is situated outside the notch. Surface deformation induces an asymmetry in the pinning potential as well as dynamical pinning. The depinning fields of the domain walls were found generally to decrease with increasing surface roughness. A DW pinned at a radial constriction creates a pinning potential well for a free DW in a parallel wire. We determined that trapped bound DW states appear above the depinning threshold and that the surface roughness facilitates the trapped bound DW states in parallel wires. Pacs : 75.60. Ch, 75.78.Cd, 75.78.Fg Nowadays, tailoring materials at the nanoscale to fabricate devices with precise functionality is an intensive area of research. A multitude of magnetic nanostructures are proposed as storage or logic devices. This devices are mainly based on moving magnetic domains separated by domain walls (DW). The motion of DWs can be controlled by magnetic field or electric current [1,2,3].Typically, device applications use ferromagnetic nanostrips (flat nanowires). To reliably control the movement of DWs in such structures, the DWs are usually pinned at notches[4] although other geo-1.

The precise manipulation of transverse magnetic domain walls in finite/infinite nanowires with artificial defects under the influence of very short spin-polarized current pulses is investigated. We show that for a classical 3d ferromagnet material like Nickel, the exact positioning of the domain walls at room temperature is possible only for pulses with very short rise and fall time that move the domain wall reliably to nearest neighboring pinning position. The influence of the shape of the current pulse and of the transient effects on the phase diagram current-pulse length are discussed. We show that large transient effects appear even when α=β, below a critical value, due to the domain wall distortion caused by the current pulse shape and the presence of the notches. The transient effects can oppose or amplify the spin-transfer torque (STT), depending on the ratio β/α. This enlarges the physical comprehension of the DW motion under STT and opens the route to the DW displacement in both directions with unipolar currents.

The nonlinear dynamics of a transverse domain wall (TDW) in Permalloy and Nickel nanostrips with two artificially patterned pinning centers is studied numerically up to rf frequencies. The phase diagram frequency -driving amplitude shows a rich variety of dynamical behaviors depending on the material parameters and the type and shape of pinning centers. We find that T-shaped traps (antinotches) create a classical double well Duffing potential that leads to a small chaotic region in the case of Nickel and a large one for Py. In contrast, the rectangular constrictions (notches) create an exponential potential that leads to larger chaotic regions interspersed with periodic windows for both Py and Ni. The influence of temperature manifests itself by enlarging the chaotic region and activating thermal jumps between the pinning sites while reducing the depinning field at low frequency in the notched strips.