Evidence for Vector Chiral Magnetic Order in κ-(BETS)₂Mn[N(CN)₂]₃

Organic CT salts have long provided ideal experimental playgrounds for studying the interplay between magnetic and charge degrees of freedom. This has culminated in the experimental discoveries of spin-liquid states in the vicinity of the Mott transition, for example in k-(ET)₂Cu₂(CN)₃ (κ-CN). Such states are thought to be stabilized by large multi-spin ring-exchange interactions. We discuss the properties of the recently synthesized κ-(BETS)₂Mn[N(CN)₂]₃ (κ-Mn). Based on analysis of specific heat, magnetic torque, and NMR measurements combined with ab-initio calculations, we will address: (i) The nature and role of π-d interactions, (ii) the magnetic interactions within the BETS layers including SOC and ring-exchange, (iii) the origin of anomalous angle dependence and therefore (iv) the character of the magnetic ground state at low pressure. In particular, we argue that all experiments and calculations support an exotic four-sublattice vector chiral order, which is selected by the combination of large ring exchange and DM interactions. Ring exchange in κ-Mn plays an opposite role as in κ-CN – namely, the ring-exchange helps to stabilize an unconventional ordered state rather than a spin-liquid.