Novel magnetic ordering in LiYbO2 probed by muon spin relaxation

The stretched diamond lattice material LiYbO2 has recently been reported to exhibit two magnetic transitions (TN1 = 1.1 K, TN2 = 0.45 K) via specific heat, magnetization, and neutron scattering measurements [Bordelon et al., Phys. Rev. B 103, 014420 (2021)]. Here we report complementary magnetic measurements down to T = 0.28 K via the local-probe technique of muon spin relaxation. While we observe a rapid increase in the zero-field muon depolarization rate at TN1, for T < TN1 we do not observe the spontaneous muon precession which is typically associated with long-range magnetic ordering. The depolarization rate in the ordered state shows a surprising sensitivity to magnetic fields applied along the initial spin polarization direction. Using a simple one-dimensional model, we show that these results are consistent with the unusual random-phase bipartite incommensurate magnetic structure proposed by Bordelon et al. for the intermediate temperature range TN2 < T < TN1. We also find evidence for magnetic fluctuations persisting to our lowest temperatures, but no obvious signature of the transition or spontaneous muon precession at and below TN2, respectively.