Spectroscopic Detection of Hopping Induced Mixed Valence for Ti and Sc in GdSc1–x Ti x O3 for x >0.165
Abstract:Only two of the first row transition metals have elemental oxides that are either ferro- or ferri-magnetic. These are CrO2 and Fe3O4. The electron spin alignment that promotes the ferro(i)magnetism is associated with a double exchange mechanism that requires mixed valence as well as metallic conductivity. This paper describes a novel way to realize these two necessary, but not sufficient conditions for double exchange magnetism. These are mixed valence and a hopping conductivity that promotes at least intra-plane electron spin alignment in a complex oxide perovskite host, A(B,C)O3. A is an ordinary metal, or a rare earth atom, B is a d0 transition metal, and C is a d n transition metal in which n ≥1, as for example in GdSc1–x Ti x O3. This article combines X-ray absorption spectroscopy, multiplet theory, charge transfer multiplet theory and degeneracy removal by Jahn-Teller effect mechanisms to demonstrate mixed valence for both Sc and Ti above a percolation threshold, x >0.16, in which hopping transport gives rise to a metal to insulator transition.
Document Type: Research Article
Publication date: 2012-06-01
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