Universal fluctuating regime in triangular chromate antiferromagnets

We report x-ray diffraction, magnetic susceptibility, heat capacity, H-1 nuclear magnetic resonance (NMR), and muon spin relaxation (mu SR) measurements, as well as density-functional band-structure calculations for the frustrated S = 3/2 triangular lattice Heisenberg antiferromagnet (TLHAF) alpha-HCrO2 (trigonal, space group: R (3) over barm). This compound undergoes a clear magnetic transition at T-N less than or similar to 22.5 K, as seen from the drop in the muon paramagnetic fraction and concurrent anomalies in the magnetic susceptibility and specific heat capacity. Local probes (NMR and mu SR) reveal a broad regime with slow fluctuations down to 0.7 T-N, this temperature corresponding to the maximum in the mu SR relaxation rate and in the NMR wipe-out. From the comparison with NaCrO2 and alpha-KCrO2, the fluctuating regime and slow dynamics below T-N appear to be hallmarks of the TLHAF with ABC stacking. We discuss the role of interlayer frustration, which may have impacted recent spin-liquid candidates with triangular geometry.

Automated summary

This study investigates the frustrated S = 3/2 triangular lattice Heisenberg antiferromagnet alpha-HCrO2 and reveals a regime with slow fluctuations below the magnetic transition temperature, as well as the impact of interlayer frustration on spin-liquid candidates with triangular geometry.