تقرير
Reduced crystal symmetry as origin of the ferroelectric polarization within the incommensurate magnetic phase of TbMn2O5
| العنوان: | Reduced crystal symmetry as origin of the ferroelectric polarization within the incommensurate magnetic phase of TbMn2O5 |
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| المؤلفون: | Narayanan, N., Graham, P. J., Rovillain, P., O'Brien, J., Bertinshaw, J., Yick, S., Hester, J., Maljuk, A., Souptel, D., Büchner, B., Argyriou, D., Ulrich, C. |
| سنة النشر: | 2021 |
| مصطلحات موضوعية: | Condensed Matter - Strongly Correlated Electrons |
| الوصف: | The precise crystal symmetry and hence the emergence of the electric polarization still remains an open question in the multiferroic materials $R$Mn$_2$O$_5$ ($R$ = rare-earth, Bi, Y). While previous diffraction studies have indicated that $R$Mn$_2$O$_5$ possesses the centro-symmetric space group P$bam$, an atomic displacement allowing for the electric polarization would require a non-centrosymmetric crystal symmetry. Our single crystal neutron diffraction experiments on TbMn$_2$O$_5$ provide direct evidence of a reduced crystallographic symmetry already above the magnetic and ferroelectric phase transitions and a change in magnetic order upon entering the ferroelectric phase. This is indicated through the presence of additional nuclear Bragg reflections that are otherwise forbidden for the space group P$bam$ but are in good agreement with the polar space group P$12_11$. It implies that the exchange-striction, which arises from a symmetric $S_i \cdot S_j$ spin coupling, is the dominating mechanism for the generation of the electric polarization in the commensurate magnetic phase of TbMn$_2$O$_5$. Furthermore, the commensurate magnetic reflections are in accordance with a quartile step spin-spiral along the $c$-axis. Therefore, the antisymmetric $S_i \times S_j$ exchange via the inverse Dzyaloshinskii-Moriya interaction contributes as well and becomes the leading term in the low temperature incommensurate spin-spiral magnetic phase. These new findings provide important information for the understanding of the complex interplay between the magnetic and the structural order throughout the $R$Mn$_2$O$_5$ series of type-II multiferroics. Comment: 27 pages, 6 figures, Supplemental Material attached |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1103/PhysRevB.105.214413 |
| URL الوصول: | http://arxiv.org/abs/2109.05164 |
| رقم الأكسشن: | edsarx.2109.05164 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1103/PhysRevB.105.214413 |
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