Nanoscale magnetic imaging using circularly polarized high-harmonic radiation

This work demonstrates nanoscale magnetic imaging using bright circularly polarized high-harmonic radiation. We utilize the magneto-optical contrast of worm-like magnetic domains in a Co/Pd multilayer structure, obtaining quantitative amplitude and phase maps by lensless imaging. A diffraction-limited spatial resolution of 49 nm is achieved with iterative phase reconstruction enhanced by a holographic mask. Harnessing the exceptional coherence of high harmonics, this approach will facilitate quantitative, element-specific, and spatially resolved studies of ultrafast magnetization dynamics, advancing both fundamental and applied aspects of nanoscale magnetism

Magnetisation switching of FePt nanoparticle recording medium by femtosecond laser pulses

Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles. We show that the magnetisation switching is a stochastic process. We develop a complete multiscale model which allows us to optimize the number of laser shots needed to switch the magnetisation of high anisotropy FePt nanoparticles in our experiments. We conclude that only angular momentum induced optically by the inverse Faraday effect will provide switching with one single femtosecond laser pulse.EC under Contract No. 281043, FemtoSpin. The work at Greifswald University was supported by the German research foundation (DFG), projects MU MU 1780/8-1, MU 1780/10-1. Research at Göttingen University was supported via SFB 1073, Projects A2 and B1. Research at Uppsala University was supported by the Swedish Research Council (VR), the Röntgen-Ångström Cluster, the Knut and Alice Wallenberg Foundation (Contract No. 2015.0060), and Swedish National Infrastructure for Computing (SNIC). Research at Kiel University was supported by the DFG, projects MC 9/9-2, MC 9/10-2. P.N. acknowledges support from EU Horizon 2020 Framework Programme for Research and Innovation (2014-2020) under Grant Agreement No. 686056, NOVAMAG. The work in Konstanz was supported via the Center for Applied Photonics

Cultural economy and the creative field of the city

I begin with a rough sketch of the incidence of the cultural economy in US cities today. I then offer a brief review of some theoretical approaches to the question of creativity, with special reference to issues of social and geographic context. The city is a powerful fountainhead of creativity, and an attempt is made to show how this can be understood in terms of a series of localized field effects. The creative field of the city is broken down (relative to the cultural economy) into four major components, namely, (a) intra-urban webs of specialized and complementary producers, (b) the local labor market and the social networks that bind workers together in urban space, (c) the wider urban environment, including various sites of memory, leisure, and social reproduction, and (d) institutions of governance and collective action. I also briefly describe some of the path-dependent dynamics of the creative field. The paper ends with a reference to some issues of geographic scale. Here, I argue that the urban is but one (albeit important) spatial articulation of an overall creative field whose extent is ultimately nothing less than global

Stability-Based Transition Transport Modeling for Unstructured Computational Fluid Dynamics at Transonic Flow Conditions

In the present work the extension of a recently published transition modeling approach is proposed. In the modified variant of the approach compressibility effects up to a Mach number of 1.6 are taken into account using the compressible formulation of the AHD transition criterion. Moreover, the Gleyzes criterion for the estimation of the transition onset location inside laminar separation bubbles was incorporated into the approach providing a higher accuracy for separation-induced transition points. The extensions were validated calculating the flat plate, the CAST10-2 airfoil and the Eppler 387 airfoil including grid resolution studies. Moreover, details with regard to the implementation and application of the extensions are given