4f−π Molecular Hybrid Exhibiting Rich Conductive Phases and Slow Relaxation of Magnetization
Yongbing Shen, Goulven Cosquer, Haitao Zhang, Brian K. Breedlove, Mengxing Cui, Masahiro Yamashita
Abstract
Cooperation between single-molecule magnets and electrical conductivity holds promise for preparing high-density magnetic devices; however, there are only a few reports so far. Here we report a 4f−π-based molecular hybrid, k-(ET)5Dy(NCS)7(KCl)0.5 (1) (ET = bis(ethylenedithio)tetrathiafulvalene, NCS— = thiocyanate), which undergoes slow relaxation of the magnetization and electrical conductivity. Unlike common ET-based conductive salts, K+ ions were intercalated into ET layers and coordinated with ET radicals. We found that the ET charges were sensitive to temperature, resulting in rich conductive phases at 75–300 K. In particular, the upturn in conductivity with a clear hysteresis loop was explained by the formation of partially oxidized states with charges close to 0.5+, which accounts for a metallic state. From the results of electronic structure calculations, the hole concentration increased to 125 K, which is consistent with a partially oxidized state upon cooling. The weak antiferromagnetic interactions accompanied by a dual magnetic relaxation process below 4 K are closely associated with the weak 4f−π interactions.