Directional dichroism in the paramagnetic state of multiferroics: A case study of infrared light absorption in Sr2CoSi2O7 at high temperatures
| Autor: | Vilmos Kocsis, J. Viirok, Yasujiro Taguchi, István Kézsmárki, Yusuke Tokunaga, Karlo Penc, Y. Tokura, D. Kamenskyi, B. Bernáth, D. G. Farkas, Sándor Bordács, P. Balla, Toomas Rõõm, D. Szaller, Urmas Nagel |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
Condensed matter physics 02 engineering and technology Dichroism 021001 nanoscience & nanotechnology 01 natural sciences Ferroelectricity Ion Condensed Matter::Materials Science Paramagnetism Phase (matter) 0103 physical sciences Multiferroics Absorption (logic) 010306 general physics 0210 nano-technology Spin (physics) |
| Zdroj: | Physical Review B. 99 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.99.014410 |
| Popis: | The coexisting magnetic and ferroelectric orders in multiferroic materials give rise to a handful of novel magnetoelectric phenomena, such as the absorption difference for the opposite propagation directions of light called the nonreciprocal directional dichroism (NDD). Usually, these effects are restricted to low temperature, where the multiferroic phase develops. In this paper, we report the observation of NDD in the paramagnetic phase of ${\mathrm{Sr}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ up to temperatures more than 10 times higher than its N\'eel temperature (7 K) and in fields up to 30 T. The magnetically induced polarization and NDD in the disordered paramagnetic phase is readily explained by the single-ion spin-dependent hybridization mechanism, which does not necessitate correlation effects between magnetic ions. The ${\mathrm{Sr}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ provides an ideal system for a theoretical case study, demonstrating the concept of magnetoelectric spin excitations in a paramagnet via analytical as well as numerical approaches. We applied exact diagonalization of a spin cluster to map out the temperature and field dependence of the spin excitations, as well as symmetry arguments of the single ion and lattice problem to get the spectrum and selection rules. |
| Databáze: | OpenAIRE |
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