Where magnetism and ferroelectricity meet: how MARVEL scientists found a very special multiferroic

This was published on October 24, 2025

In the first years of the MARVEL project, experimentalist Marisa Medarde from the Paul Scherrer Institute and theorist Nicola Spaldin at ETH Zurich started a collaboration on multiferroics - materials that combine a magnetic and a ferroelectric ordering in the same phase and that could have wide applications in electronics and memory storage. The collaboration produced a stream of discoveries and papers on a particular system, the layered perovskite YBaCuFeO5.  Marisa Medarde recalls how the material first attracted her group's attention and tells the story of how DFT calculations and experiments helped each other towards a a full experimental characterization and theoretical explanation of the material, and of how its chemical disorder can be used to modulate its multiferroic properties. This is the third article in a series about MARVEL's success stories from its 11 years of research. You can read the first one here and the second one here.

by Nicola Nosengo, NCCR MARVEL

Research on multiferroics was already a success story in its own right in the mid 2010s. These rare materials that combine both a magnetic and a ferroelectric ordering, had been on the radar of materials scientists since the early 2000s, largely thanks to seminal work by the British scientist Nicola Spaldin when she was at the University of California.

Spaldin had applied electronics structure theory to investigate why materials that are ferromagnetic and ferroelectric in the same phase are so rare. She had identified a few key electronic properties a multiferroic should have, which eventually led to the experimental demonstration of the multiferroic properties of bismuth ferrite, BiFeO3.   After that, interest in multiferroics spiked. Beyond theoretical aspects, what makes them so appealing is that their magnetisation can be manipulated by applying an electric field, and using them to store data would bring a dramatic increase in efficiency. Instead of using an electric current to generate a magnetic field and using that field to “write” data on a magnetic material, which is what we do now wasting quite a lot of energy in the process, we could skip the magnetic field and write data directly by applying an electric current field.

By the time MARVEL started in 2014, research on multiferroics was in full swing but questions still abounded, in particular on how to control their properties and use them in real-world applications. Tackling such questions required close collaboration between theorists and experimentalists, and a particularly successful one started between then MARVEL members Spaldin, who had moved to ETH Zurich in 2010, and Marisa Medarde, an experimentalist at the Paul Scherrer Institute.

The structure of the multiferroic materials YBaCuFeO5

“Multiferroics was a relatively new topic for me” recalls Medarde. “On the other hand, many of them are complex oxides, and I had worked on oxides since my own PhD, trying to understand the link between crystal structure and physical properties using neutrons and X-rays. But I had a PhD student who was interested in multiferroics, and they seemed a nice thing to investigate because the nature of the magnetic order is a key parameter for the existence of multiferroicity, and solving magnetic structures is one of my group’s specialties”.

Medarde and her team started a project on a material that looked particularly promising: the layered perovskite YBaCuFeO5. What made it interesting was the presence of a magnetic spiral, a peculiar ordering that allows magnetism and ferroelectricity to co-exist in a stable manner. Magnetic spirals normally appear only at extra cold temperatures, but this perovskite was an exception: its spiral stayed in place well above 100K.

Marisa Medarde

The first experiments by Medarde’s team brought more questions than answers, though. “Every time we prepared the sample, the critical temperature for the spiral changed” says Medarde. “This was weird compared to our previous experience with oxides. And why did the samples with larger chemical disorder have higher spiral ordering temperatures?  Chemical disorder often has the opposite effect”.   We were puzzled and could not find answers on our own”.

Medarde reached out to Spaldin and proposed a collaboration. Spaldin assigned the work to her then postdoc Andrea Scaramucci, and the two groups started having regular meetings. “It was the first time I had such a fluid and nice collaboration with a theoretician who was so interested in the experimental part” says Medarde. “Every time we met, our experiments gave them new ideas, which in turn helped us to design better experiments. It was really nice”.

The result of the collaboration, outlined in a series of papers between 2015 and 2024 (see references at the end of this article), was a full experimental charachterization and theoretical explanation of the magnetic spiral in YBaCuFeO5, and of the link between its thermal stability and the degree of chemical disorder in the material’s atomic structure. In the end, it turned out that the spiral can be stabilized up to temperatures of 100 degrees Celsius - which would make it reliable enough for commercial application – by manipulating the degree of chemical disorder in the sample, and that in turn can be done by precisely tuning the cooling rate at the manufacturing stage. 

Nicola Spaldin

“Seeing what Nicola’s team could do with DFT was eye-opening to me” says Medarde. “I became a super fan of  this technique. A good example is the calculation of the exchange constants, - needed to explain the magnetic structure. In experiments, you need to use neutrons to  get this information, and in the case of a material like this one it would take a full PhD. You need to employ instruments with different energy resolutions, the experiments are very long, and the sample has to be grown as a large, perfect single crystal.  The exchange constants calculated by Andrea were obtained in a much shorter time, and even if an experimental verification is still lacking, they can explain the existence of the magnetic spiral in YBaCuFeO5". 

Years later, stabilising multiferroism remains a challenge, and these materials have not yet reached the stage of commercial application. Medarde’s group is still studying multiferroics, and the quality of the samples has greatly improved. “At the time we mostly worked with ceramic samples that are easier to prepare”, she says. “But now the crystals have become available, and that allows us to go back to our experiments and check more things, such as the exchange constants.  Interestingly, ongoing experiments aimed to obtain these constants are so far consistent with the values calculated using DFT.  There are also groups here at PSI that are trying to manufacture thin films, which is what you need for electronics. That means most of the background is understood and you can move towards applications”.

References

M. Morin, A. Scaramucci, M. Bartkowiak, E. Pomjakushina, G. Deng, D. Sheptyakov, L. Keller, J. Rodriguez-Carvajal, N. A. Spaldin, M. Kenzelmann, K. Conder, M. Medarde, “Incommensurate magnetic structure, Fe/Cu chemical disorder, and magnetic interactions in the high-temperature multiferroic YBaCuFeO5”, Physical Review B 91, 064408 (2015). doi: 10.1103/PhysRevB.91.064408

M. Morin, T. Shang, A. Scaramucci, M. Bartkowiak, E. Pomjakushina, G. Deng, D. Sheptyakov, L. Keller, J. Rodriguez-Carvajal, N. A. Spaldin, M. Kenzelmann, K. Conder, M. Medarde, “Tuning magnetic spirals beyond room temperature with chemical disorder”, Nature Communications 7, 13758 (2016). doi: 10.1038/ncomms13758

T. Shang, A. Scaramucci, M. Bartkowiak, E. Pomjakushina, G. Deng, D. Sheptyakov, L. Keller, J. Rodriguez-Carvajal, N. A. Spaldin, M. Kenzelmann, K. Conder, M. Medarde, “Design of magnetic spirals in layered perovskites: extending the stability range far beyond room temperature”, Science Advances 4, eaau6386 (2018). doi: 10.1126/sciadv.aau6386

A. Scaramucci, H. Shinaoka, M. Mostovoy, M. Müller, C. Mudry, M. Troyer, N. Spaldin, “Multiferroic Magnetic Spirals induced by random magnetic exchanges”, Physical Review X 8, 011005 (2018). doi: 10.1103/PhysRevX.8.011005

A. Scaramucci, H. Shinaoka, M. V. Mostovoy, R. Lin, C. Mudry, M. Müller, “Spiral order from orientationally correlated random bonds in classical XY models”, Physical Review Research 2, 013273 (2020). doi: 10.1103/PhysRevResearch.2.013273

E. Marelli, J. Lyu, M. Morin, M. Leménager, T. Shang, N. S. Yüzbasi, D. Aegerter, J. Huang, N. D. Daffé, A. H. Clark, D. Sheptyakov, T. Graule, M. Nachtegaal, E. Pomjakushina, T. J. Schmidt, M. Krack, E. Fabbri, M. Medarde, “Cobalt-free layered perovskites RBaCuFeO5+δ (R = 4f lanthanide) as electrocatalysts for the oxygen evolution reaction”, EES Catalysis 2, 335 (2024). doi: 10.1039/D3EY00142C

V. Porée, D. J. Gawryluk, T. Shang, J. A. Rodríguez-Velamazań, N. Casati, D. Sheptyakov, X. Torrelles, and M. Medarde, “YBa1-xSrx⁢CuFeO5 layered perovskites: An attempt to explore the magnetic order beyond the paramagnetic-collinear-spiral triple point”, Physical Review B 110, 235156 (2024). doi: 10.1103/PhysRevB.110.235156

A. Romaguera and M. Medarde, “Room temperature magnetoelectric magnetic spirals by design”, Frontiers in Materials 11, 1448765 (2024). doi: 10.3389/fmats.2024.1448765


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