Magnetic-field-induced quantum spin liquid state in Jeff = 1/2 XY-spin rhombic lattice antiferromagnet

We propose a high LF-μSR measurement on HiFi to investigate the spin dynamics of a Jeff = 1/2 XY-spin rhombic lattice antiferromagnet KCoPO4•H2O. Preliminary µSR results at J-PARC suggest the possibility of realizing a field-induced quantum spin liquid (QSL) state. At J-PARC, only a longitudinal field (LF) of up to 0.4 T, which is lower than the phase transition field (Hc ~ 1 T), can be applied. In this experiment, we first would like to investigate the LF dependence of the muon relaxation rate from 0 T to 3 T at a temperature lower enough than the magnetic transition temperature TN = 2.8K. We believe that the information of the relaxation rate at high fields provides evidence that the field-induced QSL is realized in this compound. The goal is to complete the magnetic field-temperature phase diagram.