Imaging magnetic vortex configurations in ferromagnetic nanotubes

We image the remnant magnetization configurations of CoFeB and permalloy nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron microscopy. The images provide direct evidence for flux-closure configurations, including a global vortex state, in which magnetization points circumferentially around the NT axis. Furthermore, micromagnetic simulations predict and measurements confirm that vortex states can be programmed as the equilibrium remnant magnetization configurations by reducing the NT aspect ratio.Comment: 14 pages, 4 figures, link to supplementary informatio

Magnetization reversal of an individual exchange biased permalloy nanotube

We investigate the magnetization reversal mechanism in an individual permalloy (Py) nanotube (NT) using a hybrid magnetometer consisting of a nanometer-scale SQUID (nanoSQUID) and a cantilever torque sensor. The Py NT is affixed to the tip of a Si cantilever and positioned in order to optimally couple its stray flux into a Nb nanoSQUID. We are thus able to measure both the NT's volume magnetization by dynamic cantilever magnetometry and its stray flux using the nanoSQUID. We observe a training effect and temperature dependence in the magnetic hysteresis, suggesting an exchange bias. We find a low blocking temperature $T_B = 18 \pm 2$ K, indicating the presence of a thin antiferromagnetic native oxide, as confirmed by X-ray absorption spectroscopy on similar samples. Furthermore, we measure changes in the shape of the magnetic hysteresis as a function of temperature and increased training. These observations show that the presence of a thin exchange-coupled native oxide modifies the magnetization reversal process at low temperatures. Complementary information obtained via cantilever and nanoSQUID magnetometry allows us to conclude that, in the absence of exchange coupling, this reversal process is nucleated at the NT's ends and propagates along its length as predicted by theory.Comment: 8 pages, 4 figure

Das Paget-von Schroetter-Syndrom: Arbeitsunfall oder Berufskrankheit?

Das Krankheitsbild der "primären\u27; Thrombose der oberen Extremität im Sinne eines "Paget-von Schroetter-Syndrom\u27; (synonym: "An-strengungsthrombose\u27;, "Thrombose par effort\u27;) wird von den gesetzlichen Unfallversicherungsträgern üblicherweise weder als Arbeitsunfall noch als Berufskrankheit anerkannt. Die mehrteilige SATURN*-Studie soll klären, ob und unter welchen Kriterien die Erkrankung als Arbeitsunfall (Dauer der schädigenden Einwirkung bis zu einer Schichtlänge) oder gegebenenfalls als Berufskrankheit nach "Öffnungsklausel" (darüberhinausgehende Einwirkdauer) zu werten ist

Hydrogen Dynamics in Lightweight Tetrahydroborates

The high hydrogen content in complex hydrides such as M[AlH4]x and M[BH4]x (M = Li, Na,K, Mg, Ca) stimulated many research activities to utilize them as hydrogen storage materials. An understanding of the dynamical properties on themolecular level is important to understand and to improve the sorption kinetics. Hydrogen dynamics in complex hydrides comprise long range translational diffusion as well as localized motions like vibrations, librations or rotations. All the different motions are characterized by their specific length- and timescales. Within this review we give an introduction to the physical properties of lightweight complex hydrides and illustrate the huge variety of dynamical phenomena on selected example

Das Paget-von Schroetter-Syndrom: Arbeitsunfall oder Berufskrankheit?

Das Krankheitsbild der "primären'; Thrombose der oberen Extremität im Sinne eines "Paget-von Schroetter-Syndrom'; (synonym: "An-strengungsthrombose';, "Thrombose par effort';) wird von den gesetzlichen Unfallversicherungsträgern üblicherweise weder als Arbeitsunfall noch als Berufskrankheit anerkannt. Die mehrteilige SATURN*-Studie soll klären, ob und unter welchen Kriterien die Erkrankung als Arbeitsunfall (Dauer der schädigenden Einwirkung bis zu einer Schichtlänge) oder gegebenenfalls als Berufskrankheit nach "Öffnungsklausel" (darüberhinausgehende Einwirkdauer) zu werten ist

Bridging the Mid-Infrared-to-Telecom Gap with Silicon Nanophotonic Spectral Translation

Expanding far beyond traditional applications in optical interconnects at telecommunications wavelengths, the silicon nanophotonic integrated circuit platform has recently proven its merits for working with mid-infrared (mid-IR) optical signals in the 2-8 {\mu}m range. Mid-IR integrated optical systems are capable of addressing applications including industrial process and environmental monitoring, threat detection, medical diagnostics, and free-space communication. Rapid progress has led to the demonstration of various silicon components designed for the on-chip processing of mid-IR signals, including waveguides, vertical grating couplers, microcavities, and electrooptic modulators. Even so, a notable obstacle to the continued advancement of chip-scale systems is imposed by the narrow-bandgap semiconductors, such as InSb and HgCdTe, traditionally used to convert mid-IR photons to electrical currents. The cryogenic or multi-stage thermo-electric cooling required to suppress dark current noise, exponentially dependent upon the ratio Eg/kT, can limit the development of small, low-power, and low-cost integrated optical systems for the mid-IR. However, if the mid-IR optical signal could be spectrally translated to shorter wavelengths, for example within the near-infrared telecom band, photodetectors using wider bandgap semiconductors such as InGaAs or Ge could be used to eliminate prohibitive cooling requirements. Moreover, telecom band detectors typically perform with higher detectivity and faster response times when compared with their mid-IR counterparts. Here we address these challenges with a silicon-integrated approach to spectral translation, by employing efficient four-wave mixing (FWM) and large optical parametric gain in silicon nanophotonic wires