# Steplike metamagnetic transitions in a honeycomb lattice antiferromagnet Tb$_2$Ir$_3$Ga$_9$

## TL;DR

This study investigates the magnetic properties of Tb$_2$Ir$_3$Ga$_9$, revealing anisotropic antiferromagnetic order, field-induced spin-flip transitions, and a magnetization plateau explained by a phenomenological spin-Hamiltonian.

## Contribution

The paper presents the synthesis, magnetic characterization, and a theoretical model for understanding the metamagnetic transitions in a honeycomb lattice antiferromagnet with strong Ising anisotropy.

## Key findings

- Long-range antiferromagnetic order at 12.5 K
- Observation of two field-induced spin-flip transitions
- Presence of a magnetization plateau at half saturation

## Abstract

Single crystals of a honeycomb lattice antiferromagnet, Tb$_2$Ir$_3$Ga$_9$ were synthesized, and the physical properties have been studied. From magnetometry, a long-range antiferromagnetic ordering at $\approx$12.5 K with highly anisotropic magnetic behavior was found. Neutron powder diffraction confirms that the Tb spins lie along the $\va $-axis, parallel to the shortest Tb-Tb contact. Two field-induced spin-flip transitions are observed when the field is applied parallel to this axis, separated by a plateau corresponding roughly to M$\approx$M$_{\rm{s}}$/2. Transport measurements show the resistivity to be metallic with a discontinuity at the onset of N\'eel order. Heat capacity shows a $\lambda$-like transition confirming the bulk nature of the magnetism. We propose a phenomenological spin-Hamiltonian that describes the magnetization plateau as a result of strong Ising character arising from a quasidoublet ground state of the Tb$^{3+}$ ion in a site of \textit{C$_s$} symmetry and expressing a significant bond dependent anisotropy.