Extraordinarily large intrinsic magnetodielectric coupling of Tb member within the Haldane spin-chain family, R2BaNiO5

TL;DR

This study reports an extraordinarily large intrinsic magnetodielectric effect in Tb2BaNiO5, a Haldane spin-chain compound, driven by single-ion anisotropy, with potential implications for multiferroic materials.

Contribution

It reveals the largest intrinsic dielectric change in the R2BaNiO5 family, linked to Tb's unique anisotropy, and connects this to magnetic transitions and multiferroic behavior.

Findings

Dielectric constant changes by about 18% at 15 K in Tb2BaNiO5.

Magnetic transition at 25 K shows field-induced metamagnetic and metaelectric behavior.

Largest magnetodielectric effect observed in Tb case within the R2BaNiO5 family.

Abstract

The Haldane spin-chain compound, Tb2BaNiO5, has been known to order antiferromagnetically below (T_N= ) 63 K. The present magnetic studies on the polycrystals bring out that there is another magnetic transition at a lower temperature (T_2= ) 25 K, with a pronounced magnetic-field induced metamagnetic and metaelectric behavior. Multiferroic features are found below T_2 only, and not at T_N. The most intriguing observation is that the observed change of dielectric constant is intrinsic and largest (e.g., about 18% at 15 K) within this Haldane spin-chain family, R2BaNiO5. Taking into account that this trend (the largest change for Tb case within this family) correlates with a similar trend in T_N (with the values of T_N being about 55, 58, 53 and 32 K for Gd, Dy, Ho and Er cases), we believe that an explanation usually offered for this T_N behavior in rare-earth systems is applicable for this behavior as well . That is, single-ion anisotropy following crystal-field splitting is responsible for this extraordinary magnetodielectric effect in this Tb case. To our knowledge, such an observation was not made in the past literature of multiferroics.