New radical cation salt $κ$-(BETS)$_2$Co$_{0.13}$Mn$_{0.87}$[N(CN)$_2$]$_3$ with two magnetic metals: synthesis, structure, conductivity and magnetic peculiarities

A new metallic radical cation salt $κ$-(BETS)$_2$Co$_{0.13}$Mn$_{0.87}$[N(CN)$_2$]$_3$, where BETS is bis(ethylenedithio)tetraselenafulvalene, C$_{10}$S$_4$Se$_4$H$_8$, has been synthesized. In this salt, a part of Mn$^{2+}$ ions are replaced by Co$^{2+}$ which acts as a magnetic dopant with a different effective magnetic moment. Crystal structure, band structure, conducting and magnetic properties of the salt have been studied. Below 30 K the material undergoes a metal-insulator transition, which is suppressed by applying a pressure of ~0.5kbar, leading to a superconducting ground state. While the structural and conducting properties are very similar to those of the parent salt $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$, magnetic properties associated with localized moments in the anion layer are found to be surprisingly different.