Selective observation of sublattice magnetization in the molecular π-d system λ-(BEDT-STF)2FeCl4 studied by 13C NMR

We have performed C-13 NMR measurements on lambda-(BEDT-STF)(2)FeCl4 to reveal the mechanism of unconventional paramagneticlike behavior observed in A-type molecular pi-d systems. C-13 NMR spectra and nuclear spin-lattice relaxation rate 1/T-1 revealed that the pi and 3d electron systems undergo an antiferromagnetic transition simultaneously at 16 K with the assistance of the pi-d interaction. We found that the sublattice magnetizations of the pi and 3d spins show different temperature dependence below T-N, which is derived from the magnetic coupling between the two sublattice systems with different magnetic natures. We discuss the relationship between the two different magnetization processes and the unconventional magnetic behavior in lambda-type molecular pi-d system.