Theory of the (Remark: Graphics omitted.) Transitions Induced by Cooperative Molecular Distortions in Molecular Crystals of Iron Compounds

Abstract

The cooperative (Remark: Graphics omitted.) transitions including spin state changes in iron compounds are studied on the basis of the ligand field theory by using the model in which the coupling of the iron ion with the intramolecular distortions and the intermoleculer coupling between the molecular distortions are taken into account. The various types of thermally induced transitions between the Fe(II) high-spin ⁵T_2g, the Fe(II) low-spin ¹Al_1g, the Fe(III) high-spin ⁶A_1g, and the Fe(III) low-spin ²T_2g states are possible depending on both the relative energy position of these states in the undistorted phase and the coupling strength.