A layered conductive magnet: CrCl2(pyrazine)2 - promising new tuneable 2D material

Scientist from ISA, Department of Physics and Astronomy are involved in results that have been published in Nature Chemistry 10, 1056-1061 (2018).

2018.12.20 | Ole J. Knudsen

Target area at ISA, Aarhus University where the new results have been obtained. Photo: ZL, AU

Target area at ISA, Aarhus University where the new results have been obtained. Photo: ZL, AU

A new approach to tuneable 2D materials acting as both conductors and magnets has been made recently. Scientist from ISA, Department of Physics and Astronomy were involved in the project and the local infrastructure MatLine and AU-IR beamlines at ASTRID2 played an important rôle in understanding the electronic properties of the new material.

The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. However, almost all these 2D materials are non-magnetic up to today. Transition-metal-doped semiconductors are of particular interest for spintronics application due to their near-total spin polarization. Unfortunately, the precise distribution of metal ions is difficult to control, and spatially low-dimensional systems have not been obtained. For molecule-based systems, significant efforts have been devoted to improving and tailoring the characteristics of magnets and conductors, and a combination of these properties is typically only found in materials with separate magnetic and conductive sublattices.

Crystal structure in the 2-dimensional material

CrCl2(pyrazine)2. Illustration from the paper.

Here, we report the synthesis of CrCl2(pyrazine)2, an air-stable layered solid, by reaction of CrCl2 with pyrazine (pyz). This compound displays a ferrimagnetic order below ∼ 55 K, reflecting the presence of strong magnetic interactions. Electrical conductivity measurements demonstrate that CrCl2(pyz)2 reaches a conductivity of 32 mS cm–1 at room temperature, which operates through a 2D hopping-based transport mechanism. These properties are induced by the redox-activity of the pyrazine ligand, which leads to a smearing of the Cr 3d and pyrazine π states. We suggest that the combination of redox-active ligands and reducing paramagnetic metal ions represents a general approach towards tuneable 2D materials that consist of charge-neutral layers and exhibit both long-range magnetic order and high electronic conductivity.

The results have been published in Nature Chemistry 10, 1056-1061 (2018). The title of the paper is "Formation of the layered conductive magnet CrCl2(pyrazine)2 through redox-active coordination chemistry"

Contact:  Zheshen Li zsli@phys.au.dk

ISA, Department of Physics and Astronomy

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