Fabrication of Isolated Iron Nanowires.

Nanoscale interconnects are an important component of molecular electronics. Here we use X-ray spectromicroscopy techniques as well as scanning probe methods to explore the self-assembled growth of insulated iron nanowires as a potential means of supplying an earth abundant solution. The intrinsic anisotropy of a TiO2(110) substrate directs the growth of micron length iron wires at elevated temperatures, with a strong metal-support interaction giving rise to ilmenite (FeTiO3) encapsulation. Iron nanoparticles that decorate the nanowires display magnetic properties that suggest other possible applications.

Aberration corrected spin polarized low energy electron microscope.

Spin Polarized Low Energy Electron Microscopy (SPLEEM) is a powerful tool to reveal the magnetic structure of ferromagnetic surfaces on the atomic depth scale level[1-3]. With aberration corrected LEEM and a high brightness spin polarized electron gun, high spatial resolution will provide more details for ultra-thin ferromagnetic film studies. This study reports the first realization of aberration corrected SPLEEM (AC-SPLEEM). The performance of the setup was tested on ferromagnetic Fe nanoscale islands on a W(110) single crystal, with spatial resolution of 3.3 nm in spin asymmetry images.

Recovery of quantum efficiency in spin-polarized photocathodes by atomic hydrogen cleaning.

We demonstrate a new method of cleaning superlattice (SL) photocathodes using atomic hydrogen that allows an increased number of repeat activations. GaAs/GaAsP SL photocathodes were activated with either conventional heat cleaning or atomic hydrogen cleaning. Repeated heat cleaning was found to gradually lower the quantum efficiency (QE) of the photocathodes, while a relatively constant QE was maintained over repeated atomic hydrogen cleaning. These results show that atomic hydrogen cleaning allows a greater number of photocathode cleanings without a loss of performance. Analyses of SL photocathodes indicated that the degradation resulting from heat cleaning can likely be attributed to the build-up of residual Cs compounds as well as damage to the GaAs cap layer. The present study also determined the 1/e lifetime for a GaAs/GaAsP SL photocathode to be 7 h at an initial current of 2.2 µA.

Magnetic domain patterns on strong perpendicular magnetization of Co/Ni multilayers as spintronics materials: I. Dynamic observations.

Materials with perpendicular magnetic anisotropy can reduce the threshold current density of the current-induced domain wall motion. Co/Ni multilayers show strong perpendicular magnetic anisotropy and therefore it has become a highly potential candidate of current-induced domain wall motion memories. However, the details of the mechanism which stabilizes the strong perpendicular magnetization in Co/Ni multilayers have not yet been understood. In the present work, the evolution of the magnetic domain structure of multilayers consisting of pairs of 2 or 3 monolayers (ML) of Ni and 1 ML of Co on W(110) was investigated during growth with spin-polarized low-energy electron microscopy. An interesting phenomenon, that the magnetic domain structure changed drastically during growth, was revealed. In the early stages of the growth the magnetization alternated between in-plane upon Co deposition and out-of-plane upon Ni deposition. The change of the magnetization direction occurred within a range of less than 0.2 ML during Ni or Co deposition, with break-up of the existing domains followed by growth of new domains. The Ni and Co thickness at which the magnetization direction switched shifted gradually with the number of Co/Ni pairs. Above 3-4 Co/Ni pairs it stayed out-of-plane. The results indicate clearly that the Co-Ni interfaces play the important role of enhancing the perpendicular magnetic anisotropy.

Magnetic domain patterns on strong perpendicular magnetization of Co/Ni multilayers as spintronics materials: II. Numerical simulations.

Magnetic domains in ultrathin films form domain patterns, which strongly depend on the magnetic anisotropy. The magnetic anisotropy in Co/Ni multilayers changes with the number of layers. We provide a model to simulate the experimentally observed domain patterns. The model assumes a layer-dependent magnetic anisotropy. With the anisotropy parameter estimated from experimental data, we reproduce the magnetic domain patterns.