Broadband Setup for Magnetic-Field-Induced Domain Wall Motion in Cylindrical Nanowires

In order to improve the precision of domain wall dynamics measurements, we develop a coplanar waveguide-based setup where the domain wall motion should be triggered by pulses of magnetic field. The latter are produced by the Oersted field of the waveguide as a current pulse travels toward its termination, where it is dissipated. Our objective is to eliminate a source of bias in domain wall speed estimation while optimizing the field amplitude. Here, we present implementations of this concept for magnetic force microscopy (MFM) and synchrotron-based investigation

Magnetism in nanometer-thick magnetite

The oldest known magnetic material, magnetite, is of current interest for use in spintronics as a thin film. An open question is how thin can magnetite films be and still retain the robust ferrimagnetism required for many applications. We have grown 1-nm-thick magnetite crystals and characterized them in situ by electron and photoelectron microscopies including selected-area x-ray circular dichroism. Well-defined magnetic patterns are observed in individual nanocrystals up to at least 520 K, establishing the retention of ferrimagnetism in magnetite two unit cells thick

Switchable graphene-substrate coupling through formation/dissolution of an intercalated Ni-carbide layer

Control over the film-substrate interaction is key to the exploitation of graphene\u2019s unique electronic properties. Typically, a buffer layer is irreversibly intercalated \u201cfrom above\u201d to ensure decoupling. For graphene/Ni(111) we instead tune the film interaction \u201cfrom below\u201d. By temperature controlling the formation/dissolution of a carbide layer under rotated graphene domains, we reversibly switch graphene\u2019s electronic structure from semi-metallic to metallic. Our results are relevant for the design of controllable graphene/metal interfaces in functional devices

adsorbate induced self ordering of germanium nanoislands on si 113

The impact of Ga preadsorption on the spatial correlation of nanoscale three-dimensional (3D) Ge-islands has been investigated by low-energy electron microscopy and low-energy electron diffraction. Submonolayer Ga adsorption leads to the formation of a 2D chemical nanopattern, since the Ga-terminated (2×2) domains exclusively decorate the step edges of the Si(113) substrate. Subsequent Ge growth on such a partially Ga-covered surface results in Ge 3D islands with an increased density as compared to Ge growth on clean Si(113). However, no pronounced alignment of the Ge islands is observed. Completely different results are obtained for Ga saturation coverage, which results in the formation of (112) and (115) facets regularly arranged with a periodicity of about 40 nm. Upon Ge deposition, Ge islands are formed at a high density of about 1.3×1010 cm−2. These islands are well ordered as they align at the substrate facets. Moreover, the facet array induces a reversal of the Ge islands' shape anisotropy as compared to growth on planar Si(113) substrates

Oxygen vacancy concentration as a function of cycling and polarization state in TiN/Hf 0.5 Zr 0.5 O 2 /TiN ferroelectric capacitors studied by x-ray photoemission electron microscopy

International audienceWe have studied the field cycling behavior of microscopic TiN/Hf 0.5 Zr 0.5 O 2 /TiN ferroelectric capacitors using synchrotron-based soft x-ray photoemission electron microscopy. The oxygen vacancy ([Formula: see text]) concentration near the top TiN/Hf 0.5 Zr 0.5 O 2 interface is estimated from the reduction of Hf 4+ to Hf 3+ as measured in the Hf 4f core level spectra. The [Formula: see text] concentration increases with field cycling and redistributes under the effect of the internal field due to the polarization. Upward pointing polarization slightly depletes the concentration near the top interface, whereas downward polarization causes [Formula: see text] drift toward the top interface. The [Formula: see text] redistribution after wake-up is consistent with shifts in the I–V switching peak. The Schottky barrier height for electrons decreases systematically with cycling in polarization states, reflecting the overall increase in [Formula: see text]

Fe3S4 (greigite) formation by vapor-solid reaction

Fe3S4 (greigite), a ferrimagnetic compound widely encountered in nature and of increasing technical interest, is prepared by vapor-solid interaction. This is done in a laterally resolving ultrahigh vacuum multi-method instrument, which not only allows in situ analysis of the reaction product without influence of the environment but also follows its evolution during the reaction. The physical method employed here avoids formation of unwanted reaction products that are produced by the usual wet chemical synthesis methods. The resulting greigite crystals exhibit complex intergrowth, faceting and nanoparticle substructure and are somewhat distorted from a pure cubic symmetry. A new Curie temperature above 450 degrees C is established