1,848 research outputs found
Spin dynamics of FeGaGe studied by Electron Spin Resonance
The intermetallic semiconductor FeGa acquires itinerant ferromagnetism
upon electron doping by a partial replacement of Ga with Ge. We studied the
electron spin resonance (ESR) of high-quality single crystals of
FeGaGe for from 0 up to 0.162 where ferromagnetic order is
observed. For we observed a well-defined ESR signal, indicating the
presence of pre-formed magnetic moments in the semiconducting phase. Upon Ge
doping the occurrence of itinerant magnetism clearly affects the ESR properties
below ~K whereas at higher temperatures an ESR signal as seen in
FeGa prevails independent on the Ge-content. The present results show
that the ESR of FeGaGe is an appropriate and direct tool to
investigate the evolution of 3d-based itinerant magnetism.Comment: 12 pages, 7 figure
Hardware-aware block size tailoring on adaptive spacetree grids for shallow water waves.
Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Though they directly yield an
adaptive spatial discretisation, i.e. a mesh, it is often more efficient to augment them by regular Cartesian blocks embedded into the spacetree leaves. This facilitates stencil kernels working efficiently on homogeneous data chunks. The choice of a proper block size, however, is delicate. While large block sizes foster simple loop parallelism, vectorisation, and lead to branch-free compute kernels, they bring along disadvantages. Large blocks restrict the granularity of adaptivity and hence increase the memory footprint and lower the numerical-accuracy-per-byte efficiency. Large block sizes also reduce the block-level concurrency that can be used for dynamic load balancing. In the present paper, we therefore propose a spacetree-block coupling that can dynamically tailor
the block size to the compute characteristics. For that purpose, we allow different block sizes per spacetree node. Groups of blocks of the same size are identied automatically
throughout the simulation iterations, and a predictor function triggers the replacement of these blocks by one huge, regularly rened block. This predictor can pick up hardware characteristics while the dynamic adaptivity of the fine grid mesh is not constrained. We study such characteristics with a state-of-the-art shallow water solver and examine proper block size choices on AMD Bulldozer and Intel Sandy Bridge processors
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