Tunable Magnetic Transition to a Singlet Ground State in a 2D Van der Waals Layered Trimerized Kagom\'e Magnet

TL;DR

This study reveals a tunable magnetic phase transition in 2D Nb3X8 (X=Cl, Br) layered kagomé magnets, where a structural rearrangement induces a switch from paramagnetic to singlet ground state, with potential applications in electronic and magnetic devices.

Contribution

It demonstrates a systematic control of magnetic transition temperature and phase behavior in a family of 2D layered kagomé magnets through chemical substitution and structural analysis.

Findings

Magnetic transition from paramagnetic to singlet state observed.

Structural rearrangement accompanies magnetic phase change.

Transition temperature tunable near room temperature.

Abstract

Incorporating magnetism into two dimensional (2D) van der Waals (VdW) heterostrutures is crucial for the development of functional electronic and magnetic devices. Here we show that Nb3X8 (X = Cl, Br) is a family of 2D layered trimerized kagom\'e magnets that are paramagnetic at high temperatures and undergo a first order phase transition on cooling to a singlet magnetic state. X-ray diffraction shows that a rearrangement of the VdW stacking accompanies the magnetic transition, with high and low temperature phases consistent with STEM images of the end members {\alpha}-Nb3Cl8 and \b{eta}-Nb3Br8. The temperature of this transition is systematically varied across the solid solution Nb3Cl8-xBrx (x = 0-8), with x = 6 having transitions near room temperature. The solid solution also varies the optical properties, which are further modulated by the phase transition. As such, they provide a platform on which to understand and exploit the interplay between dimensionality, magnetism, and optoelectronic behavior in VdW materials.