Pressure-induced Spin State Transition in Co–Fe Cyanide

Abstract

Hydrostatic pressure effects on the structural and magnetic properties were investigated for two potassium–cobalt-iron hexacyanides, K_0.12Co[Fe(CN)₆]_0.70·4.87H₂O (high [Fe(CN)₆] vacancy concentration v) and K_0.36Co[Fe(CN)₆]_0.82·4.56H₂O (low-v). In both the compounds, we observed a pressure-induced volume transition at 300 K from the large volume (LV) phase to the small volume (SV) phase. In the high-v compound, the magnitude of the effective moment μ_eff gradually decreases with pressure increases. We ascribed it to the gradual spin state transformation of Co³⁺ from the high-spin state (S=2) to the low-spin state (S=0).