Molecular toroidal states have come to the forefront as candidates for next-generation quantum information devices owing to their bistability and protection from weak, short-range magnetic interactions. The protection offered by these non-magnetic vortex spin states proves to be a double-edged sword as inferring their existence in a molecular system has yet to be achieved through experimental means alone. Here, we investigate the anomalous, sickle-shaped, single-crystal magnetisation profile arising in μ-SQUID measurements of a novel CrDy₃ molecule. Theoretical modelling supported by ab initio calculations demonstrates that the weak field CrDy₃ spin dynamics is resultant from quantum superposition of the Cr^III spin states determined by three competing interactions: (i) the alignment of the Cr^III magnetic moment to the external magnetic field, (ii) the zero-field splitting of the Cr^III ground quartet, and (iii) coupling to the remnant magnetisation of the toroidal ground state in the Dy₃ triangle. If zero-field splitting of the central transition metal ion is quenched, it operates as a quantum spin sensor, which can be exploited to experimentally discriminate between ferrotoroidic and antiferrotoroidic ground states in MDy₆ double triangle complexes through electron paramagnetic resonance experiments and single-crystal magnetisation measurements with a restricted field sweeping domain.

分子环形态已成为下一代量子信息器件的候选者，因为它们具有双稳态和对弱短程磁相互作用的保护作用。这些非磁性涡旋自旋态提供的保护被证明是一把双刃剑，因为仅通过实验手段尚未推断它们在分子系统中存在。在这里，我们研究了新型 CrDy₃ 分子的 μ-SQUID 测量中出现的异常、镰刀状、单晶磁化曲线。由从头开始计算支持的理论建模表明，弱场 CrDy₃ 自旋动力学是由 Cr^III 自旋态的量子叠加产生的，该自旋态由三个竞争相互作用决定：（i） Cr^III 磁矩与外部磁场的对齐，（ii） Cr^III 接地四重奏的零场分裂， （iii） 与 Dy₃ 三角形中环形基态的残余磁化耦合。如果中心过渡金属离子的零场分裂被淬灭，它作为量子自旋传感器工作，可以利用它通过电子顺磁共振实验和限制场扫描域的单晶磁化测量，在 MDy₆ 双三角复合物中实验区分铁转子基态和反铁转子基态。