Relaxation mechanisms in the YZGO family of spin liquids

Our recently published LF-muSR study of the triangular lattice quantum spin liquid system YbZnGaO4 [PRB 106, L060401 (2022)] found that the muon spin relaxation rate measured in fields up to 0.45 T could be represented by the sum of two contributions, one dependent on field and the other independent of field. The first term was assigned to Yb ions with predominant contact hyperfine coupling to the muon, with the field dependence reflecting 2D spin diffusion, whereas the second term was assigned to Yb ions with predominant dipolar coupling to the muon. This partition of coupling types is likely to be a generic feature of this type of structure, applicable to other related systems such as YbZn2GaO5, so we wish to test this relaxation model by extending the field range of the measurements to determine whether any field dependence can be detected in the second component at fields higher than 0.45 T, which would allow us to make a further refinement of the relaxation model. Single crystal measurements will be made here to allow comparison with the powder data, allowing us also to determine the effect of anisotropy on the measured muon spin relaxation in this type of system.