Spectroscopic detection of hopping induced mixed valence for Ti and Sc in GdSc1−xTixO3 for x greater than the percolation threshold of ∼0.16

• Published in: Journal of vacuum science and technology. B, Nanotechnology & microelectronics Nanotechnology & microelectronics, 2011-01, Vol.29 (1)
• Main Authors: Lucovsky, Gerry, Miotti, Leonardo, Bastos, Karen Paz, Adamo, Carolina, Schlom, Darrell G.
• Format: Article
• Language: eng ; jpn
• ISSN: 2166-2746; 2166-2754
• DOI: 10.1116/1.3533759

Only two of the first row transition metals have elemental oxides that are either ferromagnetic or ferrimagnetic; these are CrO2 and Fe3O4. The electron spin alignment enabling ferromagnetism and/or ferrimagnetism in these oxides is associated with a double exchange mechanism that requires mixed valence and metallic conductivity. This article describes a novel way to realize these two necessary, but insufficient conditions for double exchange magnetism. These are mixed valence and a hopping conductivity that can force intraplane electron spin alignment in a complex oxide host perovskite, A(B,C)O3, where A is an ordinary metal or d0 lanthanide, B is a d0 transition metal, and C is a dn transition metal with n≥1 as, for example, in GdS1−xTixO3. 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 limit, x>0.16, in which hopping transport gives rise to a metal to insulator transition. In this alloy, ferromagnetism/ferrimagnetism is not observed due to alternating spin alignment in sequenced (Sc,Ti)O2 planes.