Properties of Mn2+ and [Pi]-Electron Spin Systems Probed by 1H and 13C NMR in the Organic Conductor [kappa]-(BETS)2Mn[N(CN)2]3

Abstract

Properties of the spin systems of the localized 3d Mn2+ ions and the conduction π electrons in quasi-two-dimensional organic conductor κ-(BETS)2Mn[N(CN)2]3 were accessed using 1H and 13C NMR in order to find their relation to the metal-insulator transition which occurs at ∼23 K. The transition of the system into the insulating state is shown to be followed by localization of the π spins into a long-range ordered staggered structure of AF type. In contrast, the 3d Mn2+ electron spin moments form a disordered tilted structure, which may signify their trend to AF order, frustrated geometrically by the triangular arrangement of Mn in the anion layer. This result suggests that the MI transition in κ-(BETS)2Mn[N(CN)2]3 is not the consequence of the interactions within the Mn2+ spins but due to the interactions within the π-electron system itself. Vice versa, it is more likelythat the disordered tilted structure of the Mn2+ spins is induced by the ordered π-spins via the π-d interaction.