Quasi-antiferromagnetic multilayer stacks with 90 degree coupling mediated by thin Fe oxide spacers

We fabricated quasiantiferromagnetic (quasi-AFM) layers with alternating antiparallel magnetization in the neighboring domains via 90 degrees magnetic coupling through an fe-o layer. we investigated the magnetic properties and the relationship between the magnetic domain size and the 90 degrees magnetic coupling via experiments and calculations. two types of samples with a ru buffer and a (ni80fe20)cr-40 buffer were prepared, and we found that with the nifecr buffer, the sample has a flatter fe-o layer, leading to stronger 90 degrees magnetic coupling and a smaller domain size compared with the ru buffer sample. this trend is well explained by the bilinear and biquadratic coupling coefficients, a(12) and b-12, in landau-lifshitz-gilbert simulations, suggesting the possibility of using both afm and fm properties by controlling the quasi-afm domain size

Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations (dataset)

This repository contains the datasets from the original smoothed particle hydrodynamics (SPH) calculations for the associated paper, including most dump files. It also includes all of the scripts for generating the figures that appear in the paper. These are contained either in the Figure_Generation.zip file or in the Paper.zip file. The former mainly contains SPLASH scripts (see below) for generating images from the SPH dump files. The latter mainly contains the final (or intermediate) SPLASH figures, plus the data files and scripts for making the other figures (line plots). Line plots use supermongo scripts. There are 5 main SPH calculations discussed in the paper, using 3 million SPH particles (3M) and with magnetic mass-to-flux ratios of 5, 10, 20, 100, and infinity (e.g. MF05). The outputs from each calculation are found in the zip files that begin with RMHD_MF*. For example, RMHD_MF05_3M.zip contains all the output (and executable) from the 3 million particle calculation with mass-to-flux ratio 5, except the dump files. The dump files are contained in a series of zip files such as: RMHD_MF05_3M_0200_0219.zip which contains 20 dump files, numbers 200 to 219. The dump files are included in groups to allow downloads in reasonably small (~20 GB) chunks, since the entire repository is ~3 TB. Also included is the output from the 1 million particle, mass-to-flux ratio 5 calculation (which was used for resolution testing in the Appendix of the paper). Only the single dump file from the 10 million particle calculation which was used to generate figure 22 is included in the respository (within the Figure_Generation.zip file) because the dump files from the entire calculation occupied another 1 TB of disk space. The SPH dump files for each calculation begin at TEST000 at time zero and then are numbered sequentially. The spacing in time is not regular (it generally decreases). The SPH dump files are Fortran binary files, written in big endian format and generated by the sphNG code. They can be read, visualised, and manipulated using the free, publicly available SPLASH visualisation code (which reads sphNG dump files), written by Daniel Price, that can be downloaded from: http://users.monash.edu.au/~dprice/splash/ Finally, the MovieAll.zip file contains the SPLASH scripts for generating the density movies associated with the paper that can be found at: http://www.astro.ex.ac.uk/people/mbate/Animations/stellarcore.htmlThis is the dataset that was used to produce the paper published in MNRAS. It contains the output from each of the SPH simulations, including dump files and the scripts used to generate the figures for the paper. To view the paper follow the DOI above or http://hdl.handle.net/10871/14622University of Exeter Visiting International Academic FellowshipMonash UniversityAustralian Research Council Discovery Project GrantEndeavour IPRS and APA postgraduate research scholarshipsUniversity of Exeter Supercomputer: jointly funded by Science and Technology Facilities Council (STFC), Large Facilities Capital Fund of BIS, and the University of ExeterDiRac Complexity computer: jointly funded by Science and Technology Facilities Council (STFC) and the Large Facilities Capital Fund of BI

Direct observation of spin diffusion enhanced nonadiabatic spin torque effects in rare-earth-doped permalloy

The relation between the nonadiabaticity parameter beta and the damping parameter alpha is investigated in permalloy-based microdisks. in order to determine beta, high-resolution imaging of the current-induced vortex-core displacement is performed using scanning electron microscopy with polarization analysis. the materials properties of the films are varied via rare-earth dy doping, leading to a greatly enhanced damping, while retaining the same spin configuration for the confined vortex state. a clear trend to much higher nonadiabaticity values is seen for the higher doping levels and an averaged value of beta = (0.29 +/- 0.15) x 10(-2) is determined for 1.73% dy doping, compared to (0.067 +/- 0.014) x 10(-2) which is extracted for pure permalloy. this is supportive of a similar scaling of beta and alpha in this system, pointing to a common origin of the spin relaxation which is at the heart of nonadiabatic transport and the dissipation of angular momentum that provides damping, in line with theoretical calculations

Direct imaging of chiral domain walls and Néel-type skyrmionium in ferrimagnetic alloys.

International audienceThe evolution of chiral spin structures is studied in ferrimagnet Ta/Ir/Fe/GdFeCo/Pt multilayers as a function of temperature using scanning electron microscopy with polarization analysis (SEMPA). The GdFeCo ferrimagnet exhibits pure right-hand Néel-type domain wall (DW) spin textures over a large temperature range. This indicates the presence of a negative Dzyaloshinskii-Moriya interaction (DMI) that can originate from both the top Fe/Pt and the Co/Pt interfaces. From measurements of the DW width, as well as complementary magnetic characterization, the exchange stiffness as a function of temperature is ascertained. The exchange stiffness is surprisingly mostly constant, which is explained by theoretical predictions. Beyond single skyrmions, we find by direct imaging a pure Néel-type skyrmionium, which due to the absence of a skyrmion Hall angle is a promising topological spin structure to enable high impact potential applications in the next generation of spintronic devices