Novel magnetic ordering in LiYbO2 probed by muon spin relaxation

TL;DR

This study uses muon spin relaxation to investigate magnetic ordering in LiYbO2, revealing unusual incommensurate structures and persistent quantum fluctuations that challenge conventional understanding of magnetic transitions.

Contribution

It provides new local probe measurements that uncover unconventional magnetic behavior and dynamics in LiYbO2, complementing previous neutron and heat capacity studies.

Findings

No spontaneous muon precession below T_N1, indicating absence of traditional long-range order.

Magnetic fluctuations persist down to lowest temperatures, suggesting quantum dynamics.

Sensitivity of depolarization rate to magnetic field implies complex magnetic structure.

Abstract

The stretched diamond lattice material LiYbO2 has recently been reported to exhibit two magnetic transitions ($T_{N1} = 1.1 K$, $T_{N2} = 0.45 K$) 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 $T_{N1}$, we do not observe any spontaneous muon precession for $T < T_{N1}$, 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 $T_{N2} < T < T_{N1}$. We also find evidence for temperature-independent magnetic fluctuations persisting to our lowest temperatures, but no obvious signature of the transition or spontaneous muon precession at and below TN2, respectively. This result is suggestive of quantum dynamics within a highly degenerate ground state.