Quantum Criticality and 2-D dissipative quantum XY ferromagnetism in single crystalline YFe2Al10 from MuSR investivations

We have performed Muon spin relaxation ($\mu$SR) measurements on single crystalline YFe$_2$Al$_{10}$ down to 19 mK and in magnetic fields up to $\sim$100 Oe with fields applied along the b-axis and c-axis. Zero-field-$\mu$SR measurements showed no evidence of magnetic order down to 19 mK, consistent with previous measurements. Interestingly we also find that the depolarization rate $\Lambda$ is temperature independent above 1 K but displays a strong diverging temperature dependence for $T <$ 1 K, different than what was observed for polycrystals of YFe$_2$Al$_{10}$. Longitudinal-field $\mu$SR measurements also reveals a time-field scaling for multiple temperatures in fields up to 200 Oe. From this work we find that single crystalline YFe$_2$Al$_{10}$ is in close proximity to a ferromagnetic quantum critical point and find evidence that it is the first experimental realization of a 2-D dissipative XY-model ferromagnet.