Dilution of the magnetic lattice in the Kitaev candidate $\hat{I}\pm$-RuCl${}_3$ by Rh${}^{3+}$ doping

Abstract

Magnetic dilution of a well-established Kitaev candidate system is realized in the substitutional Ru${}_{1-x}$Rh${}_x$Cl${}_3$ series ($x=0.02-0.6$). Optimized syntheses protocols yield uniformly-doped single crystals and polycrystalline powders that are isostructural to the parental $\hat{I}\pm$-RuCl${}_3$ as per X-ray diffraction. The Rh content $x$ is accurately determined by the quantitative energy-dispersive X-ray spectroscopy technique with standards. We determine the magnetic phase diagram of Ru${}_{1-x}$Rh${}_x$Cl${}_3$ for in-plane magnetic fields from magnetization and specific-heat measurements as a function of $x$ and stacking periodicity, and identify the suppression of the magnetic order at $x\approx 0.2$ towards a disordered phase, which does not show any clear signature of freezing into a spin glass. Comparing with previous studies on the substitution series Ru${}_{1-x}$Ir${}_x$Cl${}_3$, we propose that chemical pressure would contribute to the suppression of magnetic order especially in Ru${}_{1-x}$Ir${}_x$Cl${}_3$ and that the zigzag magnetic ground state appears to be relatively robust with respect to the dilution of the Kitaev--$\hat{I}“$--Heisenberg magnetic lattice. We also discovered a slight dependence of the magnetic properties on thermal cycling, which would be due to an incomplete structural transition.