Magnetic ground state of honeycomb magnet BaCo2(P1-xVx)2O8

The Kitaev model, which deals with S = 1/2 spins connected by bond-dependent spin-spin interaction on a honeycomb lattice, has been paid much attention because of its remarkable prediction of the ground state such as a spin-liquid state with gapless excitation of Majorana fermions. Recently, honeycomb cobalt oxide BaCo2(P1-xVx)2O8 (BCPVO) is promising as a new candidate for realizing Kitaev physics. In a previous study, a spin-glass (SG) transition is reported for x = 0.15 and 0.20 samples, whereas an antiferromagnetic (AF) transition occurs in x > 0.30 samples. However, our detailed dc magnetization experiment suggests that the reentrant SG and AF transitions is expected for x > 0.30 samples. This proposed muon spin rotation/relaxation experiment is the first investigation of the ground state of BCPVO by local spin probe and it will clarify the interesting ground state of BCPVO.