# Successive phase transitions and quantum magnetization plateau in the spin-1 triangular-lattice antiferromagnet Ba$_2$La$_2$NiTe$_2$O$_{12}$

## TL;DR

This study investigates the magnetic properties and phase transitions of a spin-1 triangular-lattice antiferromagnet Ba$_2$La$_2$NiTe$_2$O$_{12}$, revealing successive magnetic transitions, a quantum magnetization plateau, and significant exchange interactions via experiments and DFT calculations.

## Contribution

It provides the first detailed analysis of the magnetic phase transitions and quantum magnetization plateau in Ba$_2$La$_2$NiTe$_2$O$_{12}$, highlighting differences from tungsten analogs and confirming two-dimensional magnetic behavior.

## Key findings

- Successive magnetic phase transitions at 9.8 K and 8.9 K.
- Observation of a one-third magnetization plateau.
- Large exchange interaction and good two-dimensionality confirmed by DFT.

## Abstract

The crystal structure and magnetic properties of the spin-1 triangular-lattice antiferromagnet Ba$_2$La$_2$NiTe$_2$O$_{12}$ are reported. Its crystal structure is trigonal $R\bar{3}$, which is the same as that of Ba$_2$La$_2$NiW$_2$O$_{12}$ [Y. Doi et al., J. Phys.: Condens. Matter 29, 365802 (2017)]. However, the exchange interaction $J/k_{\mathrm{B}}\simeq19$ K is much greater than that observed in the tungsten system. At zero magnetic field, Ba$_2$La$_2$NiTe$_2$O$_{12}$ undergoes successive magnetic phase transitions at $T_{\mathrm{N}1}=9.8$ K and $T_{\mathrm{N}2}=8.9$ K. The ground state is accompanied by a weak ferromagnetic moment. These results indicate that the ground-state spin structure is a triangular structure in a plane perpendicular to the triangular lattice owing to the small easy-axis-type anisotropy. The magnetization curve exhibits the one-third plateau characteristic of a two-dimensional triangular-lattice Heisenberg-like antiferromagnet. Exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate the large difference in the exchange constants between tellurium and tungsten systems and the good two-dimensionality of the tellurium system.