Two-photon Lithography for 3D Magnetic Nanostructure Fabrication

Ferromagnetic materials have been utilised as recording media within data storage devices for many decades. Confinement of the material to a two dimensional plane is a significant bottleneck in achieving ultra-high recording densities and this has led to the proposition of three dimensional (3D) racetrack memories that utilise domain wall propagation along nanowires. However, the fabrication of 3D magnetic nanostructures of complex geometry is highly challenging and not easily achievable with standard lithography techniques. Here, by using a combination of two-photon lithography and electrochemical deposition, we show a new approach to construct 3D magnetic nanostructures of complex geometry. The magnetic properties are found to be intimately related to the 3D geometry of the structure and magnetic imaging experiments provide evidence of domain wall pinning at a 3D nanostructured junction

Photoelectrochemical imaging of non-planar surfaces : the influence of geometrical and optical factors on image formation

In situ scanning photoelectrochemical (PEC) microscopy is a technique for mapping the photocurrent stimulated by a focused light at an electrode-electrolyte interface. This technique gives position-sensitive information on the nature of passivating films (composition, type and degree of crystallization, thickness, etc) that cover metal electrodes. In the analysis of PEC images, further aspects related to the surface shape and/or surface irregularities (roughness, slope errors, surface waviness, etc) have to be taken into account. In this paper we present the effects of non-planar surfaces by measuring the photoresponse of passivating oxide films on cylindrical iron rods with different diameters. The variation of the angle of incidence of the light, as the laser beam scans the surface of the rod, implies either a change in the spot size and different optical response of the oxide-metal system, such as the transmittivity of the oxide, the reflectivity of the metal and the light path inside the film. For evaluating the behaviour of the photocurrent, we have simulated these geometrical and optical effects by using a simple model in geometrical optics approximation. Images have been also acquired at various distances from the beam focus for highlighting the degradation of the spatial resolution induced by the focusing misalignment of the curved samples

Characterization and hardness of Co−P coatings obtained from direct current electrodeposition using gluconate bath

Direct current electrodeposition of Co−P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co−P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390 °C in DSC profiles of Co−P coatings could be attributed to the crystallization and formation of Co2P phase in the coatings. Asdeposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P (Pδ−) as well as oxidized P (P5+) are present on the surface of coatings. Concentrations of Co metal and Pδ− increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co−P coating obtained from 10 g L−1 NaH2PO2 is heated at 400 °C that is comparable with hard chromium coatings