New mechanism allows superconductivity and magnetism to coexist in the same material



Physicists from the University of Bath, in association with scientists in the United States, have revealed a new mechanism that allows superconductivity and magnetism to exist together in the same material.

Left: A gold coated crystal – the gold coating allows the magnetic imaging tool to come within nanometers of the material’s surface. Right: a magnetic image of a segment of the crystal showing the vortices (black holes) that have been studied. Image credit: University of Bath.

To date, investigators could only guess at the viability of this unique coexistence. The new discoveries could lead to the development of superconducting devices, such as advanced computer hardware, and lead to new applications in green energy technologies.

Generally, magnetism (noticed at work in fridge magnets) and superconductivity (i.e. the potential of a material to pass electricity with ideal efficiency) do not make excellent companions because the alignment of microscopic electronic magnetic particles present in ferromagnetics usually damages the electron. pairs responsible for superconductivity.

But despite this, researchers at the University of Bath found that RbEuFe4As4—The iron-based superconductor which is superconducting at less than -236 ° C – exhibits both magnetism and superconductivity at less than -258 ° C.

There is a state in some materials where, if you really cool them, much cooler than Antarctica, they become superconducting. But for this superconductivity to be applied to higher level applications, the material must show a coexistence with magnetic properties..

David Collomb, Study Director and Postdoctoral Research Student in Physics, University of Bath

This would allow us to develop devices operating on a magnetic principle, such as magnetic memory and computation using magnetic materials, to also take advantage of the advantages of superconductivity.Added Collomb.

The problem is that superconductivity is usually lost when magnetism is activated. For many decades, scientists have tried to explore a multitude of materials that have both properties in a single material, and materials scientists have recently succeeded in making a handful of these materials. However, until we understand why coexistence is possible, the hunt for these materials cannot be done with such a fine comb..

David Collomb, Study Director and Postdoctoral Research Student in Physics, University of Bath

This new research gives us a material that has a wide temperature range where these phenomena coexist, and it will allow us to study more closely and in more detail the interaction between magnetism and superconductivity. Hopefully this will allow us to identify the mechanism by which this coexistence can occur., added Mr. Collomb.

To study the extraordinary behavior of RbEuFe4As4, the researchers produced magnetic field maps of a superconducting material as the temperature decreased. The study was published in the Physical examination letters newspaper.

But to their amazement, the researchers found that the vortices (that is, the points in the superconducting material into which the magnetic field penetrates) showed pronounced broadening near a temperature of -258 ° C. This indicated a strong inhibition of superconductivity when magnetism activated.

Such observations correspond to a hypothetical model recently suggested by Dr Alexei Koshelev of the Argonne National Laboratory in the United States. This concept explains how superconductivity is suppressed by magnetic changes due to europium (Eu) atoms in crystals.

In this case, the magnetic direction of each atom of Eu begins to vary and align with other atoms as the material decreases below a specific temperature. This makes the material magnetic. Researchers at the University of Bath have thus concluded that although it is considerably weakened by the magnetic effect, superconductivity is not completely destroyed.

This suggests that in our material, magnetism and superconductivity are separated from each other in their own sub-networks, which interact only minimally., added Mr. Collomb.

This work considerably advances our understanding of these rare coexisting phenomena and could lead to possible applications in superconducting devices of the future. This will lead to a deeper hunt in materials that exhibit both superconductivity and magnetism. We hope this will also encourage researchers in more applied fields to take some of these materials and turn them into next-generation computing devices..

David Collomb, Study Director and Postdoctoral Research Student in Physics, University of Bath

Hopefully, the scientific community will gradually enter an era where we move from researching blue skies to making devices from these materials. In ten years or so, we could see prototypes of devices using this technology that do a real job., concluded Mr. Collomb.

The American collaborators in this study were the Argonne National Laboratory, Northwestern University and Hofstra University.

Journal reference:

Collomb, D., et al. (2021) Observation of superconductivity suppression in RbEuFe4As4 by correlated magnetic fluctuations. Physical examination letters.




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