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Guru Venkat, 02/25/2015 08:49 AM


Proposal for a Standard Micromagnetic Problem: Spin Wave Dispersion in a Magnonic Waveguide

G. Venkat, D. Kumar, M. Franchin, O. Dmytriiev, M. Mruczkiewicz, H. Fangohr, A. Barman, M. Krawczyk and A. Prabhakar

online: journal, local preprint pdf (SW_standard_problem_Pre_print.pdf)

Motivation

  • The micromagnetic standard problems (www.ctcms.nist.gov/~rdm/stdplan.html) allow to compare the simulation results of different simulation tools and help finding bugs and errors.
  • Here we propose a new standard problem that computes spin wave dispersion of a permalloy stripe using different micromagnetic packages

Summary

  • We propose a standard micromagnetic problem which involves a nanostripe of permalloy
  • The magnetization dynamics is studied and methods to extract features from simulations are described. The image below shows spin waves propagating as a function space and time.

Spin wave propgation in the stripe

  • Spin wave dispersion curves, relating frequency and wave vector, are obtained for wave propagation in different configurations
  • Simulation results obtained using both finite element (Nmag) and finite difference (OOMMF) packages are compared against analytic results

Selected results

The dispersion curves compared against the analytic equations (dotted lines).

Dispersion curves along the length of the stripe

Supporting material

  1. The Nmag mesh - The mesh file (nanowire.nmesh.h5). It has been generated using the Examesh utility (examesh.zip) which can be used for generating the mesh for a cuboid structure.
  2. The Nmag simulation script - The simulation script (run.py) has details of the simulation. The comments in it should be self explanatory. Notice that it uses the HLib library for compressing the BEM matrix generated during the simulation
  3. The Nmag post processing script - The post processing script (post_process.py) generates the spin wave space-time and dispersion plots from the simulation data. It is assumed that Numpy and matplotlib are both available.
  4. The Makefile for the Nmag simulation - This Makefile should run the entire simulation and then generate the dispersion curves. We strongly suggest this sort of approach because it reduces manual effort and the chances of errors.
  5. README - A README file (README.txt) describes the action of the above Makefile
  6. The OOMMF simulation scripts - The relaxation script (OOMMF_static.mif) and the dynamics script (OOMMF_dynamics.mif) should help in setting up an OOMMF simulation to obtain dispersion curves.

All the files are included in this zip file (attachment:spin_wave_dispersion_standard_problem.zip)

SW_standard_problem_Pre_print.pdf - Pre print of the paper (1.11 MB) Guru Venkat, 04/15/2013 09:12 AM

Dispersions_scaled.png - Dispersion curves along the length of the stripe (397 KB) Guru Venkat, 04/15/2013 10:44 AM

SW_scaled.png - Spin wave propgation in the stripe (218 KB) Guru Venkat, 04/16/2013 02:43 AM

OOMMF_static.mif - OOMMF static simulation file (1.14 KB) Guru Venkat, 02/25/2015 08:54 AM

OOMMF_dynamics.mif - OOMMF dynamics simulation file (1.81 KB) Guru Venkat, 02/25/2015 08:54 AM

stripe_simulation.zip - All the files for the Nmag simulation (261 KB) Guru Venkat, 02/25/2015 11:01 AM

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