Destruction of multiferroicity in Tb2BaNiO5 by Sr doping and its implication to magnetoelectric coupling

TL;DR

This study investigates how Sr doping in Tb2BaNiO5 affects its multiferroic properties, revealing the destruction of ferroelectricity while magnetic order persists, and highlighting the importance of ferroelectricity for magnetoelectric effects.

Contribution

It demonstrates that Sr doping suppresses ferroelectricity in Tb2BaNiO5, providing insights into the interplay between ferroelectricity and magnetoelectric coupling in this compound.

Findings

Ferroelectricity is lost at 10% Sr doping.

Magnetodielectric behavior persists but is reduced.

Ferroelectric order is essential for large magnetoelectric effects.

Abstract

The Haldane spin-chain compound, Tb2BaNiO5, with two antiferromagnetic transitions, one at T1=63K, and the other at T2=25K, has been recently shown by us to be an exotic multiferroic below T2. Here, we report the results of our investigations of Sr doping at the Ba site by magnetization, heat-capacity, magnetoelectric (MDE), and pyrocurrent measurements. An intriguing finding, which we stress, is that the ferroelectricity is lost even for a doping level of 10 atomic percent, though magnetic ordering prevails. The doped specimens however retain significant magnetodielectric behaviour, but with reduced magnitudes and qualitative changes with respect to the behaviour of the parent compound. This implies that ferroelectric order is also crucial for the anomalously large MDE in the parent compound, in addition to the role of 4f single-ion anisotropy.