Pressure-temperature phase diagram for charge-transfer transition in Cs[Co(3-CNpy)_2][W(CN)_8]H_2O

摘要

Effects of the hydrostatic pressure on the magnetic and structural properties are investigated in a charge-transfer material, Cs[Co(3-CNpy)_2][W(CN)_8]H_2O (CNpy≈cyanopyridine), with two-dimensional Co-W network bridged by CN anions. We have found that the compound shows a pressure-induced charge-transfer (CT) transition at 0.5 GPa at room temperature, accompanied by a remarkable color change from transparent red to green. The upper critical temperature (T_(CT,up)) for the CT transition increases at a huge rate of 250 K/GPa under pressures, reflecting the concomitant significant volume change (ΔV/V= 0.08).