# A N\'eel-type antiferromagnetic order in the spin 1/2 rare-earth honeycomb YbCl$_3$

## TL;DR

This study investigates YbCl3, a honeycomb lattice material with Yb3+ ions, revealing Nel-type antiferromagnetic order and potential for Kitaev physics exploration due to its effective spin-1/2 moments and magnetic properties.

## Contribution

The paper presents the first detailed experimental characterization of YbCl3's magnetic order and anisotropy, proposing it as a promising candidate for Kitaev physics research.

## Key findings

- Yb3+ ions exhibit a Kramers doublet ground state with effective spin 1/2.
- YbCl3 shows short-range order below 1.20 K and Nel-type antiferromagnetic order at 0.60 K.
- Magnetic order can be suppressed by magnetic fields, indicating tunable magnetic properties.

## Abstract

Most of the searches for Kitaev materials deal with $4d/5d$ magnets with spin-orbit-coupled ${J=1/2}$ local moments such as iridates and $\alpha$-RuCl$_3$. Here we propose the monoclinic YbCl$_3$ with a Yb$^{3+}$ honeycomb lattice for the exploration of Kiteav physics. We perform thermodynamic, $ac$ susceptibility, angle-dependent magnetic torque and neutron diffraction measurements on YbCl$_3$ single crystal. We find that the Yb$^{3+}$ ion exhibits a Kramers doublet ground state that gives rise to an effective spin ${J_{\text{eff}}=1/2}$ local moment. The compound exhibits short-range magnetic order below 1.20 K, followed by a long-range N\'eel-type antiferromagnetic order at 0.60 K, below which the ordered Yb$^{3+}$ spins lie in the $ac$ plane with an angle of 16(11)$^{\circ}$ away from the $a$ axis. These orders can be suppressed by in-plane and out-of-plane magnetic fields at around 6 and 10 T, respectively. Moreover, the N\'eel temperature varies non-monotonically under the out-of-plane magnetic fields. The in-plane magnetic anisotropy and the reduced order moment 0.8(1) $\mu_B$ at 0.25 K indicate that YbCl$_3$ could be a two-dimensional spin system to proximate the Kitaev physics.