Detuning the Honeycomb of the α-RuCl₃ Kitaev Lattice: A Case of Cr₃₊ Dopant

Fine-tuning chemistry by doping with transition metals enables new perspectives for exploring Kitaev physics on a two-dimensional (2D) honeycomb lattice of α-RuCl 3 , which is promising in the field of quantum information protection and quantum computation. The key parameters to vary by doping are both Heisenberg and Kitaev components of the nearest-neighbor exchange interaction between the J eff = 1 / 2 Ru 3+ spins, depending strongly on the peculiarities of the crystal structure. Here, we present crystal growth by chemical vapor transport and structure elucidation of a solid solution series Ru 1-x Cr x Cl 3 (0 ≤ x ≤ 1), with Cr 3+ ions coupled to the Ru 3+ Kitaev host. The Cr 3+ substitution preserves the honeycomb type lattice of α-RuCl 3 and creates mixed occupancy of Ru/Cr sites without cationic order within the layers as confirmed by single-crystal X-ray diffraction and transmission electron microscopy investigations. In contrast to high-quality single crystals of α-RuCl 3 with ABAB-stacked layers, the ternary compounds demonstrate a significant stacking disorder along the c-axis direction as evidenced by X-ray diffraction and high resolution scanning transmission electron microscopy (HR-STEM). Raman spectra of substituted samples are in line with the symmetry conservation of the parent lattice upon chromium doping. At the same time, our magnetic susceptibility data indicate that the Kitaev physics of α-RuCl 3 is increasingly suppressed by the dominant spin-only driven magnetism of Cr 3+ (S = 3 / 2 ) in Ru 1-x Cr x Cl 3 . © 2019 American Chemical Society