Introducing and implementing micromagnetic simulation techniques in the study of magnetic materials
User-friendly computational models are key to take neutron science to the next level. But today many researchers lack both the tools and the time to apply more refined theoretical models in their own work. Two LINXS workshops on magnetic materials aim to introduce numerical simulation techniques and methods, and discuss possibilities of how to implement them in small angle neutron scattering and reflectometry.
Andreas Michels, is associate professor in Physics and Materials at the University of Luxemburg, and member of the Magnetic Material working group, under the theme New Materials.
Small angle neutron scattering techniques and reflectometry are important methods to study magnetism and magnetic materials. This includes a broad range of material classes such as soft magnetic nanocomposites, permanent magnets, magnetic steels, ferrofluids, nanoparticles, magnetic oxides, thin films, or skyrmion crystals and long-range ordered magnetic structures.
– To analyse your scattering data you need a model. It is not enough to have your interesting sample, your neutron technique; you also need a theoretical model. But the underlying equations are often so difficult and complex that you cannot write down their solution on a piece of paper; you must use numerical computation, says Andreas Michels, associate professor in Physics and Materials at the University of Luxemburg, and member of the Magnetic Material working group.
Growing interest to create and apply more refined models
He explains that within the small angle neutron scattering community there has been a growing interest to create and apply more and more refined computational models based on the theory of micromagnetism to scattering data sets. The interest has been mostly driven by individual researchers – and the computer codes that exist for SANS analysis were written, not with the user in mind, but with an aim to understand a problem.
– What neutron science needs, in my view, is a dedicated effort to develop computer models that are user friendly, and that can be taken up by the community. One strategy would be to fund post-docs to develop simulation tools and present them in such a way they are picked up and used.
He continues:
– PhD-students and post-docs are under enormous pressure; they need to write papers and finish their projects in a certain rigid time frame. Besides your interesting sample, which you want to understand, you also have to make an enormous investment to apply these theoretical models. That can be hard in your daily life, and means that many people use easy but simplified approaches. But these are often crude and miss the fine details.
Hope to initiate interesting discussions on implementation
Andreas Michels hopes that the two workshops will produce interesting discussions on how one can start to implement the use of computational simulation techniques – both in small angle neutron scattering and in reflectometry.
– My dream is that we achieve a critical mass of people who can use these more refined micromagnetic simulations. Otherwise, we will not progress our research on magnetic materials sufficiently.
Andreas Michels has been using small angle neutron scattering for 20 years. He explains that many of the early analytical models have emerged from small angle x-ray scattering, where a well-developed theoretical framework has been developed. But, neutron science, and especially the analysis of magnetic materials, needs more refined models.
– Even though change has been sluggish, people are now slowly realizing that a simplified approach is limited – something I am glad to see.
Another aim of the workshops is to bring the small angle scattering community and the reflectometry community closer together.
– So far these two communities have not spoken much with each other. There is everything to gain from a deeper collaboration, especially since computational codes for neutron scattering could be used by many other research communities too, he concludes.
The workshops