Department of Physics and Astronomy

Magnetic materials for green energy technology

Olle Eriksson. Photo: Camilla Thulin.

Main goals and expected outcomes

We propose to explore new magnetic materials in two technologies; magnetic refrigeration and power conversion using renewable sources. The attention of a cross-disciplinary team will be divided equally for scientific questions of these two emerging fields. We expect to identify several new materials with improved properties for either of these two technologies, and a swift transfer of the obtained results to the industrial partners of this proposal.

The uncertainty in availability of rare-earth elements is a serious threat to green technologies for the transport sector or for the generation of electrical energy. Several consortia in Europe, USA and Japan have realized this and focus large efforts in finding alternatives to conventional rare-earth permanent magnets (effectively the Nd-Fe-B magnets). The most challenging aspect is to identify rare-earth free magnets (REFM) with a sufficiently large magnetocrystalline anisotropy, large saturation moment and high ordering temperature. We will address this by combining efforts from academia with an industrial partner (Höganäs AB), in a cross disciplinary team that covers expertise from ab initio theory, to materials synthesis and characterization, as well as system aspects and potential for commercialization. We expect to identify several alternatives to the most commonly used permanent magnets, with competing prize performance.

The magnetocaloric effect (MCE) is the magneto-thermodynamical phenomenon that manifests in the heating of a magnetic material in response to the application of an external magnetic field. Magnetocaloric heat pumps used in refrigeration need 50% less energy compared to vapor-compression based technology. The most important MCE parameters of a magnetocaloric material are the adiabatic temperature change ΔTad(T, H) and the magnetic entropy change ΔSm(T, H). Unfortunately, very little is known as to what makes a magnetic material suitable for this technology. Together with an industrial partner (Sandvik Materials Technology of Sandvik AB) we will outline the mechanisms that make a magnetic material efficient for cooling applications, in order to optimize the so-called magnetocaloric effect (MCE). This effort will involve ab initio theory coupled to atomistic spin-lattice dynamics simulations, materials synthesis and characterization, as well as system aspects and potential for commercialization. In addition to fine-tuning the properties of the recently identified Fe-Mn-P-Si and LaFe13-based compounds, we expect to identify entirely new classes of magnets that don’t rely on critical elements, and have improved magnetocaloric properties (large temperature and entropy changes when modest magnetic field are applied < 2T).

Both as concerns REFM and MCE materials we will explore the idea of the materials genome, in which large scale materials simulations are combined with genetic and evolutionary algorithms. The aim to identify new, functional magnetic materials then becomes a scientific question where data mining algorithms are suitable, something we have previous experience with. This enables screening amongst hundreds of thousands of compounds, in order to identify a smaller group of materials (20-40) that have the highest potential for a specific application. In this step one often finds entirely new compounds that have not previously been discussed. We envision passing information from the theoretical screening part to the experimental partners of this proposal that will synthesize and characterize these materials. Here it is expected that a group of two to three commercially competitive REFM and two to three new compounds for MCE applications will emerge, and be made available for the industrial partners of this proposal.  

Throughout this project we expect a close collaboration amongst members of a scientific team with competence in materials theory, as well as experimental synthesis and characterization. The team has affiliation in physics, engineering science and chemistry at Uppsala University, materials science at KTH, and at the R&D divisions at Sandvik and Höganäs. Training of the next generation materials scientists is an important component of this proposal.