Wallenberg Scholar Olle Eriksson has put together a world-leading environment in the field of materials theory at the Ångström Laboratory in Uppsala. He is using mathematical models and computer simulations to study magnetic and other materials to predict their functionality and improved applications. The research team hopes to identify new, less expensive and more environmentally friendly magnetic materials, and also to continuously refine theoretical methods describing the materials.

“The Wallenberg Scholar grant is unique, since it enables researchers to address major unresolved questions. Our research would not have the same impact without it, and we would not be able to keep pace with the international competition.”

Strongly magnetic materials are currently based on rare earth metals such as neodymium. But almost all mines producing those metals are in China, and their price fluctuates. There is great concern that technology is being made dependent on a raw material that will become too expensive and difficult to obtain.

“And the mining operations are extremely harmful to the environment, so there are several reasons why there is a growing interest in finding alternative magnetic materials. It’s essential if we are to achieve a transition to green energy,” Eriksson says.

New magnetic materials could also make electronics faster, with lower energy consumption, and increase information storage capacity. This is why the researchers want to identify new metal combinations, and are using mathematics in their search.

“Our calculations are based on a number of quantum mechanical equations that we are able to execute with the help of supercomputers, particularly the Swedish National Infrastructure for Computing (SNIC), which is an extraordinarily important resource for Swedish researchers.”

Describing the dynamics of electrons

The mathematics is based on the Schrödinger Equation, which describes the dynamics of particles, for instance electrons. A few years ago the Uppsala researchers created an entire database on the electron structure of the materials.

“We concentrate on how the electrons move in materials. Electron movement is what gives rise to all the chemical bonds that stabilize materials, and explains, for example, why iron is magnetic, glass is transparent, and why our DNA strands are arranged as they are,” Eriksson explains.

The electron structure describes the properties of the material, and may be said to be the material’s own DNA. The database contains information on over 100,000 materials, including iron, aluminum, and silicon. The next step is for the researchers to select materials with attractive properties, and simulate them in films. This is a way of “discovering” them virtually on the computer.

“We have published an alloy of iron and cobalt with desirable properties. But one problem is that cobalt is not especially cheap, so that material probably doesn’t offer a future solution.”

Alloys of iron and nickel are another combination offering great potential. These are inexpensive and environmentally acceptable, but there are some difficulties, particularly in synthesizing the material.

“Iron and nickel atoms are unruly, and tend to lie higgledy-piggledy on the crystal lattice. The challenge we face is to get them to lie in the right place.”

Following theoretical predictions and synthesis of new compounds, the material is passed on to other researchers for experimental trials.

But other lines of research are also in progress, including skyrmions, a magnetic phenomenon that may revolutionize electronics of the future. Skyrmions are swirling topological defects in the magnetization structure that may be stable in several materials. They can be made extremely small, and polarized by spin-polarized currents that can be steered in the desired direction.

“We hope to use skyrmions as information carriers, since they have a unique inner structure, or topology, a discovery recognized by the Nobel Prize in Physics in 2016.”

Magnetic cooling

Another line of research is magnetic cooling, a field that has existed for nearly 100 years, but whose applications have so far been too expensive for regular households. The technology may be illustrated by the element gadolinium, which heats up each time it is exposed to a magnetic field, and cools when the field disappears, with a change in temperature of about 4 degrees Celsius.

“This technology could replace compressor-based refrigeration, but first we need to find better materials,” Eriksson comments.

The potential is huge. Experiments using an iron-rhodium crystal have shown that energy consumption could be half that needed to run regular compressor-based refrigerators. But the drawback is the high price of the material.

“Diamonds would be cheap in comparison.”

Eriksson is convinced that the research will ultimately contribute to solutions to current environmental and energy problems. But he is not primarily driven by the needs of society – his main impetus comes from an irrepressible curiosity and a desire to answer fundamental scientific questions.

“Most of all we want to resolve difficult problems, and also test and develop models. Naturally, it is a bonus if our findings lead to useful practical applications.”

Text Nils Johan Tjärnlund
Translation Maxwell Arding
Photo Magnus Bergström