Anisotropic Kitaev Spin Glass in Li₂Ru_(x)Ir_(1-x)O₃

Kitaev iridates have emerged as an important class of spin-orbit-entangled quantum materials in which bond-directional exchange interactions generate strong magnetic frustration and unconventional correlated states. Rather than realizing simple ordered magnets, members of the alpha,beta,gamma-Li2IrO3 family exhibit fragile and highly anisotropic magnetic behavior, including incommensurate counter-rotating order, strong field sensitivity, and pressure-driven electronic reconstruction. These phenomena place the iridates in close proximity to the Kitaev quantum spin liquid (QSL) regime, while simultaneously revealing the importance of competing interactions, lattice distortions, and spin-orbit-assisted hopping processes beyond the ideal Kitaev limit. Understanding how chemical substitution perturbs these competing interactions provides a route toward probing the underlying frustrated magnetic state. Here, we study single crystals of beta-Li2RuxIr1-xO3 with dilute Ru substitution, x<~10%. Through a combination of magnetometry, resonant elastic X-ray scattering, ac-heat capacity, and muon spin relaxation/rotation, we show that weak magnetic disorder continuously suppresses the incommensurate antiferromagnetic ground state without stabilizing an alternative long-range ordered phase. Instead, the system evolves into a bulk static spin glass characterized by slow relaxation, aging behavior, and frozen local magnetic fields. Despite the loss of long-range magnetic order, the glassy state retains substantial directional anisotropy without significant distortion to the honeycomb lattice, suggesting that disorder freezes spins within a still-active bond-directional exchange environment. In this picture, dilute Ru substitution provides a controlled pathway into an anisotropic Kitaev spin glass regime that preserves essential fingerprints of the underlying Kitaev exchange network.