Short-range quasistatic order and critical spin correlations in alpha-Ru1-xIrxCl3

The magnetic ground states of the diluted alpha-Ru1-xIrxCl3 are systematically investigated by magnetization, specific heat, and muon spin rotation measurements. Introduction of moderate spin vacancies leads to a destabilization of the zigzag antiferromagnetic order towards a short-range ordered state. It is remarkable that the x = 0.2 sample located near a quantum critical point shows an extremely short correlation length of the magnitude of magnetic moments zeta(mag) similar to 1.2a (a = lattice spacing) and a power-law behavior of the magnetic susceptibility chi(T)similar to T-P below 14 K for mu H-0 parallel to ab and below 30 K for mu H-0 parallel to c. Our work demonstrates that the alpha-Ru1-xIrxCl3 system hosts a short-range, quasistatic order characterized by critical spin correlations.