Magnetic field induced transition in the charge-glass former θ−(BEDT−TTF)2CsCo(SCN)4

We perform thermodynamic and transport measurements on a magnetic charge-glass former, $\ensuremath{\theta}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}\mathrm{CsCo}{(\mathrm{SCN})}_{4}$, to discuss the $\ensuremath{\pi}\ensuremath{-}d$ interaction occurring in the interlayer direction. An anomalous temperature dependence and sharp peak structure of the heat capacity are observed in magnetic fields, indicating a field-induced transition in this compound. Furthermore, a sharp peak of the thermoelectric power is also observed in magnetic fields, supporting the presence of the field-induced transition. Comparison with a nonmagnetic analog compound indicates that the introduction of magnetic ${\mathrm{Co}}^{2+}$ ions $(S=3/2)$ triggers this transition. This strongly suggests that the $\ensuremath{\pi}\ensuremath{-}d$ interaction effectively works in this compound and affects the physical properties. To explain the field-induced phenomenon in this compound, we propose a speculative scenario in which the $\ensuremath{\pi}\ensuremath{-}d$ interaction between the $\ensuremath{\pi}$ spins in the insulating domains and the $d$ spin of ${\mathrm{Co}}^{2+}$ induces the reconstruction of the domain structure in the CG state.