Ferroelectricity driven by magnetism in quasi-one-dimensional Ba9Fe3Se15

TL;DR

This paper reports the discovery of spin-induced ferroelectricity in the quasi-one-dimensional compound Ba9Fe3Se15, driven by short-range spin orders that lead to magnetoelectric effects above the long-range spin order temperature.

Contribution

It demonstrates that short-range spin orders can induce ferroelectricity and dynamic responses in quasi-1D systems, a phenomenon not observed in three-dimensional counterparts.

Findings

Ferroelectricity occurs above the long-range spin order temperature.

Short-range spin orders are key to the observed ferroelectricity.

The compound exhibits magnetoelectric coupling far above TN.

Abstract

The spin-induced ferroelectricity in quasi-1D spin chain system is little known, which could be fundamentally different from those in three-dimensional (3D) system. Here, we report the ferroelectricity driven by a tilted screw spin order and its exotic dynamic in the spin-chain compound Ba9Fe3Se15. It is found that the spin-induced polarization has already occurred and exhibits magnetoelectric coupling behavior far above the long-range spin order (LRSO) at TN = 14 K. The polarized entities grow and their dynamic responses slow down gradually with decreasing temperature and permeate the whole lattice to form 3D ferroelectricity at TN. Our results reveal that the short-range spin orders (SRSOs) in the decoupled chains play a key role for the exotic dynamic in this dimension reduced system. Ba9Fe3Se15 is the only example so far which exhibits electric polarization above LRSO temperature because of the formation of SRSOs.