Non-linear vortex dynamics and transient effects in ferromagnetic disks

We report a time resolved imaging and micromagnetic simulation study of the relaxation dynamics of a magnetic vortex in the non-linear regime. We use time-resolved photoemission electron microscopy and micromagnetic calculations to examine the emergence of non-linear vortex dynamics in patterned Ni80Fe20 disks in the limit of long field pulses. We show for core shifts beyond ~20-25% of the disk radius, the initial motion is characterized by distortions of the vortex, a transient cross-tie wall state, and instabilities in the core polarization that influence the core trajectories.Comment: 11 pages, 3 figures, submitted to Phys. Rev. Let

Magnetic Vortex Core Dynamics in a Ferromagnetic Dot

We report direct imaging by means of x-ray photoemission electron microscopy of the dynamics of magnetic vortices confined in micron-size circular Permalloy dots that are 30 nm thick. The vortex core positions oscillate on a 10-ns timescale in a self-induced magnetostatic potential well after the in-plane magnetic field is turned off. The measured oscillation frequencies as a function of the aspect ratio (thickness/radius) of the dots are in agreement with theoretical calculations presented for the same geometry.Comment: 18 pages including 4 figure

Antiferromagnetic Domain Wall Engineering in Chromium Films

We have engineered an antiferromagnetic domain wall by utilizing a magnetic frustration effect of a thin iron cap layer deposited on a chromium film. Through lithography and wet etching we selectively remove areas of the Fe cap layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe locally removes magnetic frustration in user-defined regions of the Cr film. We present x-ray microdiffraction microscopy results confirming the formation of a 90{\deg} spin-density wave propagation domain wall in Cr. This domain wall nucleates at the boundary defined by our Fe mask.Comment: submitted to AP

Reddening law and interstellar dust properties along Magellanic sight-lines

This study establishes that SMC, LMC and Milky Way extinction curves obey the same extinction law which depends on the 2200A bump size and one parameter, and generalizes the Cardelli, Clayton and Mathis (1989) relationship. This suggests that extinction in all three galaxies is of the same nature. The role of linear reddening laws over all the visible/UV wavelength range, particularly important in the SMC but also present in the LMC and in the Milky Way, is also highlighted and discussed.Comment: accepted for publication in Astrophysics and Space Science. 16 pages, 12 figures. Some figures are colour plot

Physical parameters of IPHAS-selected classical Be stars. (I. Determination procedure and evaluation of the results.)

Reproduced with permission from Astronomy & Astrophysics, © 2016 ESOWe present a semi-automatic procedure to obtain fundamental physical parameters and distances of classical Be (CBe) stars, based on the Barbier-Chalonge-Divan (BCD) spectrophotometric system. Our aim is to apply this procedure to a large sample of CBe stars detected by the IPHAS photometric survey, to determine their fundamental physical parameters and to explore their suitability as galactic structure tracers. In this paper we describe the methodology used and the validation of the procedure by comparing our results with those obtained from different independent astrophysical techniques for subsamples of stars in common with other studies. We also present a test case study of the galactic structure in the direction of the Perseus Galactic Arm, in order to compare our results with others recently obtained with different techniques and the same sample of stars. We did not find any significant clustering of stars at the expected positions of the Perseus and Outer Galactic Arms, in agreement with previous studies in the same area that we used for verification.Peer reviewedFinal Published versio

Nonlinear Vortex Dynamics and Transient Domains in Ferromagnetic Disks

We report a time-resolved imaging and micromagnetic simulation study of the relaxation dynamics of a magnetic vortex in the nonlinear regime. We use time-resolved photoemission electron microscopy and micromagnetic calculations to examine the emergence of nonlinear vortex dynamics in patterned Ni80Fe20 disks in the limit of long field pulses. We show for core shifts beyond ∼20%–25% of the disk radius, the initial motion is characterized by distortions of the vortex, a transient cross-tie wall state, and instabilities in the core polarization that influence the core trajectories

Nonlinear Vortex Dynamics and Transient Domains in Ferromagnetic Disks

We report a time-resolved imaging and micromagnetic simulation study of the relaxation dynamics of a magnetic vortex in the nonlinear regime. We use time-resolved photoemission electron microscopy and micromagnetic calculations to examine the emergence of nonlinear vortex dynamics in patterned Ni80Fe20 disks in the limit of long field pulses. We show for core shifts beyond ∼20%–25% of the disk radius, the initial motion is characterized by distortions of the vortex, a transient cross-tie wall state, and instabilities in the core polarization that influence the core trajectories

How do research-intensive universities portray employability strategies? A review of their websites

© Australian Council for Educational Research 2017. Employability development is a strategic priority for universities across advanced western economies. Despite this, there is no systematic study of employability development approaches internationally. In this study, we considered how universities portray employability on the public pages of their websites. We undertook website content analysis of 107 research-intensive universities in Australia, Canada, the United Kingdom and the United States. Following Farenga and Quinlan, we classified these strategies as Portfolio, Hands-off, Award and Non-embedded. Portfolio or Award strategies were the most common across all four locations; Hands-off and Non-embedded strategies were more common to US universities; and Award was more common in the United Kingdom. Universities focused on either possessional or positional approaches to employability. We advocate for a pedagogical shift towards processual approaches in which responsibility for employability development is shared