Random singlets in the s=5/2 coupled frustrated cubic lattice Lu3Sb3Mn2O14

Abstract

We combine thermodynamic, electron spin resonance (ESR), and muon spin-relaxation ($\mathrm{\ensuremath{\mu}}\mathrm{SR}$) measurements with density functional theory (DFT) and classical Monte Carlo calculations toward understanding a disorder-driven behavior of the 3D coupled frustrated cubic lattice $\mathrm{Lu}{}_{3}\mathrm{Sb}{}_{3}\mathrm{Mn}{}_{2}{\mathrm{O}}_{14}$ with $s=5/2$. The classical Monte Carlo calculations based on exchange interactions extracted from DFT predict that $\mathrm{Lu}{}_{3}\mathrm{Sb}{}_{3}\mathrm{Mn}{}_{2}{\mathrm{O}}_{14}$ undergoes a transition to magnetic ordering. In sharp contrast, our specific heat measurements evince a weak magnetic anomaly at 0.5 K while $\mathrm{\ensuremath{\mu}}\mathrm{SR}$ detects neither long-range magnetic order nor spin freezing down to 0.3 K. For temperatures above 2 K, our $\mathit{ac}$ susceptibility, magnetization, and specific heat data obey temperature-magnetic field scalings, indicative of the formation of 3D random singlets. The development of multiple ESR lines with decreasing temperature below 80 K supports the notion of inhomogeneous magnetism. Our results extend random-singlet physics to 3D frustrated classical magnets with a large spin number $s=5/2$.