American Chemical Society
nn9b04392_si_001.cif (9.64 kB)

Tunable Magnetic Transition to a Singlet Ground State in a 2D van der Waals Layered Trimerized Kagomé Magnet

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posted on 2019-07-22, 18:40 authored by Christopher M. Pasco, Ismail El Baggari, Elisabeth Bianco, Lena F. Kourkoutis, Tyrel M. McQueen
Incorporating magnetism into two-dimensional (2D) van der Waals (vdW) heterostructures 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 kagomé 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 scanning transmission electron microscopy images of the end members α-Nb3Cl8 and β-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.