Associate Professor Rasmus Bjørk, DTU Energy

New project will result in stronger magnets

Monday 04 Feb 19


Rasmus Bjørk
Head of Section
DTU Energy
+45 46 77 58 95

About the project

The project “Solving Brown’s paradox in micromagnetism” is supported by Poul Due Jensens Foundation to the amount of 3.56 million DKK. The project manager is Associate Professor Rasmus Bjørk. The project will employ a PhD student and a postdoc and will last 3.5 years.

The Poul Due Jensen Foundation

The Poul Due Jensen Foundation is a Danish industrial foundation. It is the main owner of the pump company Grundfos and was established by the Grundfos founder, Poul Due Jensen. The foundation supports three philanthropic themes: Water, Research and Inclusion.
An ambitious project at DTU Energy will find the reason that permament magnets in practice only are half as strong as predicted theoretically. The results of the projects will make it possible to utilize the expensive materials used for the magnets better. The project is supported by the Poul Due Jensen Foundation, owner of the Danish pump company Grundfos.

All electrical motors contain magnets – either electromagnets, where the magnetic field is created by an electrical current, or permanent magnets. The latter are more expensive than electromagnets but also result in more efficient motors. For this reason they are found in electrical devices everywhere: from washing machines, pumps and electric cars to giant generators in wind turbines.

Usually you want to as powerful magnets as possible; then they may be made smaller and you save expensive magnet material. However, the magnetic fields from the different magnets in, e.g., an electrical motor can be so large that one or more magnets are demagnetized by the field from the other magnets. If this happens, the motor will not work. The resistance of a magnet against being demagnetized is measured by a quantity called the coercivity. Researchers worldwide are trying to come up with ways to increase the coercivity of magnets. For instance it is necessary to add the expensive metal dysprosium to the widely used neodynium magnets to increase their coercivity.

But a fundamental scientific problem stands in the way of a systematic optimization of magnet properties: We still do not konw the specific physical and chemical factors that determine the coercivity of a magnet. Indeed, the strength of actual magnets are only half as large as predicted by theory.

Now, in a project supported by the Poul Due Jensen Foundation, Associate Professor Rasmus Bjørk from DTU Energy will tackle this problem using a new approach. Rasmus Bjørk has previously worked on magnets and magnet optimization but he is also an expert in 3D modelling of the microstructure of solids. And it is exactly by combining magnetism and 3D microstructure that Rasmus wants to make progress.

“Until now it has only been possible to do calculations on idealised structures which do not correspond to the microstructure of actual materials. In the project we are going to develop a model which will be able to capture the microstructure of a permanent magnet as realistically as possible. In this way we will be able to identify the most important factors limiting the coercivity of permanent magnets”, Rasmus Bjørk says.

And he is already looking at the next step: to develop strategies to improve the coercivity by design of the microstructure of the magnets.

For the Poul Due Jensen Foundation Rasmus's project is a good example of how excellent research can go hand in hand with applications and societal relevance:

“We at the Poul Due Jensen Foundation are very happy to support a project which is driven by the elementary curiosity of an unsolved scientific problem, but also has very concrete perspectives as regards minimizing the use of rare metals like dysprosium in electrical motors", states Executive Director Kim Nøhr Skibsted.

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