Successive magnetic phase transitions and multiferroicity in Spin-1 triangular lattice antiferromagnet Ba$_3$NiNb$_2$O$_9$

TL;DR

This study investigates Ba$_3$NiNb$_2$O$_9$, a quasi-2D spin-1 triangular lattice antiferromagnet, revealing successive magnetic phase transitions and multiferroic behavior linked to different magnetic orders.

Contribution

It reports the discovery of multiple magnetic phases and associated ferroelectricity in Ba$_3$NiNb$_2$O$_9$, demonstrating its multiferroic properties linked to specific magnetic states.

Findings

Identification of 120° magnetic order at low T

Observation of up-up-down phase at 1/3 saturation magnetization

Detection of ferroelectricity at phase boundaries

Abstract

We report the magnetic and electric properties of Ba$_3$NiNb$_2$O$_9$, which is a quasi-two-dimensional spin-1 triangular lattice antiferromagnet (TLAF) with trigonal structure. At low $T$ and with increasing magnetic field, the system evolves from a 120 degree magnetic ordering phase (A phase) to an up-up-down ($uud$) phase (B phase) with a change of slope at 1/3 of the saturation magnetization, and then to an "oblique" phase (C phase). Accordingly, the ferroelectricity switches on at each phase boundary with appearance of spontaneous polarization. Therefore, Ba$_3$NiNb$_2$O$_9$ is a unique TLAF exhibiting both $uud$ phase and multiferroicity.