Dilution of the magnetic lattice in the Kitaev candidate α−RuCl3 by Rh3+ doping

Abstract

Magnetic dilution of a well-established Kitaev candidate system is realized in the substitutional ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{\mathrm{Cl}}_{3}$ series $(x=0.02--0.6)$. Optimized syntheses protocols yield uniformly doped single crystals and polycrystalline powders that are isostructural to the parental $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ 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 ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{\mathrm{Cl}}_{3}$ 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 $x\ensuremath{\approx}0.2$ 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 ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Ir}}_{x}{\mathrm{Cl}}_{3}$, we propose that chemical pressure would contribute to the suppression of magnetic order, especially in ${\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Ir}}_{x}{\mathrm{Cl}}_{3}$, and that the zigzag magnetic ground state appears to be relatively robust with respect to the dilution of the Kitaev-$\mathrm{\ensuremath{\Gamma}}$-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.