Magnetism in the Jeff= 12 kagome antiferromagnet Nd3BWO9: Thermodynamics, nuclear magnetic resonance, muon spin resonance, and inelastic neutron scattering studies

The intertwining of competing degrees of freedom, anisotropy, and frustration induced strong quantum fluctuations offers an ideal ground for realizing exotic quantum phenomena in the rare-earth based kagome lattice. Herein, we report the synthesis, structure, thermodynamic, muon spin relaxation (μSR), nuclear magnetic resonance (NMR), and inelastic neutron scattering (INS) studies of a frustrated quantum magnet Nd3BWO9 (NBWO), wherein Nd3+ ions constitute a distorted kagome lattice. The INS experiments on NBWO allow us to establish a detailed crystal electric field (CEF) spectrum. The magnetic susceptibility reveals the presence of two energy scales in agreement with the INS results, wherein the higher-energy state is dominated by the thermal population of CEF excitations. The lowest Kramers ground-state doublet is well separated from the excited state, suggesting that the compound realizes a low-energy Jeff=12 state at low temperatures. The low-energy state is witnessed via thermodynamic results that reveal an anomaly at 0.3 K typical of a phase transition, which is attributed to the presence of complex magnetic ordering phenomena. The broad maximum in the specific heat well above 0.3 K indicates the presence of short-range spin correlations. The isothermal magnetization reveals a field-induced 13 magnetization plateau at low temperatures. μSR relaxation rate experiments, on the other hand, neither show the signature of a phase transition nor spin freezing down to 34 mK. The zero-field μSR relaxation rate is governed by an Orbach process and reveals the presence of fluctuating moments owing to the depopulation of crystal field levels, reflected as a constant value of the relaxation rate in the temperature range 0.04 ≤ T ≤ 10 K. NMR results indicate the presence of fluctuating Nd3+ moments down to 1.8 K, consistent with μSR experiments. Our comprehensive results reveal that a field-induced quantum phenomenon is at play, exemplifying the proximity effect of competing magnetic states and the coexistence of static and fluctuating moments along with short-range spin correlations in this frustrated kagome magnet. The broad rare-earth RE3BWO9 family of frustrated kagome magnets is a promising candidate for hosting exotic quantum states driven by spin-orbit coupling and frustration.