Stabilization of highest-oxidation states of transition metals and the induced electronic phenomena in oxidic perovskite structures
Résumé
In oxides the stabilization of the highest oxidation states n+ of transition metals leads to the stabilization of strong covalent Mn+-O bonds. Such very covalent bonds can induce electronic phenomena as spin transitions through the increase of the local crystal-field energy (Dq) or in the specific case of an anisotropic eg1 electronic configuration some strong interactions with the perovskite structure (3D character, structural distortion) can lead to a insulatormetal transition or a disproportionation phenomenon. [2Mn+(M(n - )+)+(M(n+)+)] In order to illustrate such a topic, three unusual oxidation states have been selected: Co3+(d6), Fe4+(d4) and Ni3+(d7) in perovskite-type structures.