Investigation of possible quantum spin liquid ground state in d4 iridium double perovskite PrSrMgIrO6 using muon-spin-rotation/relaxation

A new series of Ir-based double perovskites Pr2-xSrxMgIrO6 (x = 0, 0.5, 1) has been theoretically proposed to undergo a transition from the spin-orbit-coupled Mott insulating phase at x = 0 to the elusive half-metallic antiferromagnetic (HMAFM) state with Sr doping at x = 1. But, in contrary to such claim, our detailed magnetic, electrical, and x-ray photoemission spectroscopy measurements clearly refute HMAFM ground state in either of the doped samples. Rather, we have evidenced that the correlated magnetic behaviors of each of these compounds are solely governed by the Ir-moments, while the magnetic Pr3+ only contributes to the total paramagnetic moments. While, there is clear indication of magnetic ordering transition for the x = 0 and 0.5 samples, the half-Sr-doped (x = 1) d4 iridate DP PrSrMgIrO6 (PSMIO) evades any magnetic transition till down to 2 K despite significant antiferromagnetic interaction, thus promoting the PrSrMgIrO6 material towards a potential quantum spin-liquid candidate. Therefore, we here propose to perform the in-depth microscopic local probe muon-spin-relaxation/rotation (µSR) experiments on PSMIO till down to 50 mK in order to confirm the true magnetic ground state and the ground state spin dynamics.