Abstract
The understanding of the superconducting phase under pressure in the famous iron-based spin ladder commands a perfect understanding of the structural properties. We present an accurate single crystal x-ray analysis which demonstrates that the structure admitted until now at room temperature is totally ruled out. We show that the system has a polar structure already at 300 K and is thus ferroelectric. Its structure is modified below the Néel transition and the polarization is intensified. These features unambiguously prove the multiferroic character of as proposed theoretically. This system evidences a competition between multiferroicity and superconductivity.
- Received 10 May 2019
- Revised 25 October 2019
DOI:https://doi.org/10.1103/PhysRevB.101.020101
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