Shuhei Fukuoka, Atsushi Kawamoto
Chemistry Letters 51 4 375 - 385 2022年02月01日
[査読有り] Organic conductors consisting of donor and anion molecules provide various important study fields such as superconductivity and electron correlation. pi electrons are responsible for the emergence of these phenomena. On the other hand, the coexistent systems of pi electrons and localized 3d spins have been realized by introducing magnetic anions. Such coexistent systems are called pi-d systems. In pi-d systems, various fascinating magnetic and conducting phenomena are observed due to the coupling of pi electrons and localized 3d electrons (pi-cl interaction). One of the most striking phenomena is magnetic field-induced superconductivity, which is first observed in X-(BETS)(2) FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene. On the other hand, X-(BETS)(2)FeCl4 shows a metal-insulator transition accompanying an antifeffomagnetic ordering at TN of 8.3 K and the unconventional antifeffomagnetic state that 3d spins behave as if they stay paramagnetic even below TN. These phenomena are also considered to be caused by the pi-cl interaction, but their mechanisms have not been demonstrated.Recently, a new lambda-type pi-cl system of lambda-(BEDT-STF)(2)FeCl4, where BEDT-STF is bis(ethylenedithio)dithiadiselenafulvalene, has been developed. In this review, the influence of bandwidth control by donor substitution and the dilution effect of magnetic ions on the magnetic properties of the pi-d system will be discussed. We will demonstrate that site-selective magnetization measurements by C-13 NMR and Fe-57 Mossbauer measurements and heat capacity measurements provide important information to understand the mechanism of unconventional magnetic properties in pi-d systems. We would also like to introduce the advantages of the C-13 NMR measurements using one-sided C-1(3)-enriched donor molecules, which are the key technique in our experiments.