Aller au contenu directement

Controlling the Magnetic Properties of the van der Waals Multiferroic Crystals Co1–xNixI2

Published on June 17, 2024

The structurally related compounds NiI2 and CoI2 are multiferroic van der Waals materials in which helimagnetic orders exist simultaneously with electric polarization. Here, we report on the evolution of the crystal structure and of the magnetic properties across solid solution Co1–xNixI2. We have successfully grown crystals of the whole range of the solid solution, i.e., x = 0–1, by employing the self-selecting vapor growth (SSVG) technique and by carefully tuning the synthesis conditions according to the chemical composition. Our structural investigations show that the crystal symmetry changes from Pm1 to Rm when Ni substitutes for Co beyond x = 0.2. Both the lattice parameters and magnetic properties evolve continuously and smoothly from one end member to the other, showing that they can be finely tuned by the chemical composition. We also observe that the degree of Ni substitution in the solid solution affects the metamagnetic transition typical for CoI2 at high magnetic fields. In particular, we find the existence of a metamagnetic transition similar to that for CoI2 in the NiI2 structure. Based on magnetic measurements, we construct the phase diagram of the Co1–xNixI2 system. Controlling the magnetic properties by the chemical composition may open new pathways for the fabrication of electronic devices made of two-dimensional (2D) flakes of multiferroic van der Waals materials.


Anastasiia Lukovkina, Sara A. López-Paz, Céline Besnard, Laure Guenee, Fabian O. von Rohr, and Enrico Giannini

Published in

Chem. Mater. 2024