A new hypothesis on the curious features of europium-based multiferroic material

|

Thanks to their peculiar properties, there’s a growing interest in the last decade around multiferroic materials. In particular, their magnetic properties can be tuned by an electric field and vice versa. These features make them an exciting playground for studying new physics and chemistry. Furthermore, they could be a platform for developing new technologies in areas like nano-electronics, spintronics, and more recently, solar cells and photocatalysis. In this regard, a specific multiferroic material, EuTiO3 (ETO), has raised the scientific community’s interest.

Dr. Panagiotis Pappas (National Technical University of Athens) and colleagues analysed ETO samples with several analytical techniques encountering puzzling results. They found that around 282 K (8,85 °C), a morphological phase transition from cubic to tetragonal is revealed by X-ray diffraction (XRD), but curiously, no Raman modes were found contrary to the homologous SrTiO3 (STO). Experiments were performed at the XRD1, MCX, and IUVS beamlines, available at the Italian CERIC Partner Facility at the Elettra synchrotron, and at the XAS beamline at the Polish CERIC Partner Facility at the Solaris synchrotron. During such tests, the authors also discovered that some Raman modes in ETO samples could be activated by applying hydrostatic pressure or an external magnetic field.

Raman spectra of EuTiO3 under 200 mT DC magnetic field reveal the activation of a mode indicative of the structural phase transition in remarkable agreement with theoretical predictions. Also hydrostatic pressure above 4.1 GPa activates the same mode

These results suggest that a possible explanation for the puzzling absence of Raman modes could be related to the magnetic europium (Eu) ions. Such hypothesis would explain the lack of Raman modes as well as their activation following external perturbations. Further investigations on this and other multiferroic materials could allow the discovery of new chemistry/physics with potential applications in strategic technological sectors.

ORIGINAL ARTICLE:

MAGNETIC INTERACTIONS AND THE PUZZLING ABSENCE OF ANY RAMAN MODE IN EUTIO3, PAPPAS P., LIAROKAPIS E., CALAMIOTOU M., BUSSMANN-HOLDER A., JOURNAL OF RAMAN SPECTROSCOPY, 2021.