Benchmarks or standard problems are well defined (often computational) tasks for which results are available to compare with. Benchmarks can be used to validate new codes against known correct results, or compare a number of results from different groups and techniques.
In the micromagnetic community, the National Institute of Standards and Technology has initiated the collection of such micromagnetic standard problems [1], and made 4 such problems together with solutions from a variety of groups and codes available.
The Southampton micromagnetic modelling group has developed and contributed two more problems that address (i) micromagnetic systems driven with a spin-polarised current, and (ii) studies of dispersion relations as done in the emerging field of magnonics.
(i) the combination of conventional micromagnetics with the Zhang-Li Spin-torque transfer term is studied for a well defined problem using OOMMF, M3S, Nmag and analytical methods, with partners fromt the University of Hamburg (Germany) and IBM Zuerich (Switzerland). We propose to a standard problem system to be a permalloy cuboid of 100 nm edge length in x and y direction,and 10 nm thickness, which contains a Landau pattern with a vortex in the center of the structure. A spin-polarized dc current density of 10^12 A/m^2 flows laterally through the cuboid and moves the vortex core to a new steady-state position. We show that the new vortex-core position is a sensitive measure for the correctness of micromagnetic simulators that include the spin-transfer torque. We compute, show and compare numerical results from four different finite-difference and finite-element-based simulation tools. We also show the solution of an approximate but analytical model.
(ii) The spin wave dispersion in a magnonic waveguide is studied with partners from India and Poland. Dispersion relations are important to design the next generation of signal processing logic based on low-energy magnetic information carrier technology, and increasingly researchers in academia and industry use micromagnetic packages to compute those. This publication [4] details how the dispersion relation can be extracted from conventional micromagnetic dynamics simulations, and provides a particular example that can be used to validate against.
[1] Standard Problems
[4] Proposal for a Standard Micromagnetic Problem: Spin Wave Dispersion in a Magnonic Waveguide
