Mesa+ Institute develops magnetic material with preferred orientation

The Mesa+ Institute of the University of Twente has investigated a new combination of ferromagnetic materials in collaboration with various institutes around the world. This offers opportunities for spintronics, but also for mram, for example.

Mark Huijben of Mesa+ explains exactly what was discovered. “We have carried out very fundamental research in materials science. It could be applied to mram, for example, but for us it is all about the new atomic control of the material itself,” says Huijben. “At the University of Twente, we can make very controlled thin layers in our nanolab. We can make films that are only an atomic layer thick. If you can do that, you can also influence the crystal structure very well. That structure ultimately determines whether the material is magnetic or electrical. conductive.”

“This material, lanthanum-strontium magnate, is normally ferromagnetic. We have vapor deposited that material so that it has a precise order. The magnetic material thus acquires a preferred direction for magnetism. In that crystal structure there is an atom with six oxygen atoms around it. “These oxygen atoms can collectively have a certain direction of rotation. Now we have taken a crystalline underlayer with a rotation in those oxygen atoms. We then put a layer with that ferromagnetic material over it, so that those oxygen atoms also get the same rotation in it.”

“We also call them Legos with atoms,” continues Huijben. “We have put layers on top of each other so that the structure from the layer below continues into the layer above. If we put one atomic layer of another material between those materials, the ferromagnetic layer no longer takes over the rotation of the oxygen atoms. the magnetic layer is no longer coupled to the underlying material and the direction of the magnetism is different. And the special thing is: only one atom layer is enough to switch off that coupling.”

It is an interesting discovery that only one atom layer is already sufficient to cancel the influence on magnetism by the rotation of the oxygen atoms. Huijben explains exactly what you can do with it. “You can then create a surface where that one atomic layer is or is not present,” he explains. “The direction of the magnetism is then perpendicular to each other between those different areas. In this way you can create very different small areas to, for example, write data, perhaps for mram.”

“A second possibility is to give a layer of magnetic material a preferential direction and to place a magnetic layer on top of it that is at right angles to the other. That is interesting for spintronics. With such combinations you can think of higher switching speeds. The following The next step is to find out whether that really works.” “These are only initial steps,” concludes Huijben. “People had been looking for a long time to create two layers with perpendicular magnetism.” That now seems to have indeed worked.

The Mesa+ Institute could not do this alone. In Antwerp, the atomic cross-sections of the layers were made, in Canada the cross-section was looked at at the magnetism level, and then there was an Austrian group that supported the theoretical model. The entire research appeared in Nature Materials.