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Electronic structure of negative charge transfer CaFeO 3 across the metal-insulator transition

DOI: 10.1103/PhysRevMaterials.2.015002 DOI Help

Authors: Paul C. Rogge (Drexel University) , Ravini U. Chandrasena (Temple University) , Antonio Cammarata (Czech Technical University) , Robert J. Green (University of British Columbia; University of Saskatchewan) , Padraic Shafer (Advanced Light Source) , Benjamin M. Lefler (Drexel University) , Amanda Huon (Drexel University; Oak Ridge National Laboratory) , Arian Arab (Temple University) , Elke Arenholz (Advanced Light Source) , Ho Nyung Lee (Oak Ridge National Laboratory) , Tien-lin Lee (Diamond Light Source) , Slavomir Nemsak (Forschungszentrum Jülich GmbH; Advanced Light Source) , James M. Rondinelli (Northwestern University) , Alexander Gray (Temple University) , Steven J. May (Drexel University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review Materials , VOL 2

State: Published (Approved)
Published: January 2018
Diamond Proposal Number(s): 17824

Abstract: We investigated the metal-insulator transition for epitaxial thin films of the perovskite CaFeO3, a material with a significant oxygen ligand hole contribution to its electronic structure. We find that biaxial tensile and compressive strain suppress the metal-insulator transition temperature. By combining hard x-ray photoelectron spectroscopy, soft x-ray absorption spectroscopy, and density functional calculations, we resolve the element-specific changes to the electronic structure across the metal-insulator transition. We demonstrate that the Fe sites undergo no observable spectroscopic change between the metallic and insulating states, whereas the O electronic configuration undergoes significant changes. This strongly supports the bond-disproportionation model of the metal-insulator transition for CaFeO3 and highlights the importance of ligand holes in its electronic structure. By sensitively measuring the ligand hole density, however, we find that it increases by ∼5–10% in the insulating state, which we ascribe to a further localization of electron charge on the Fe sites. These results provide detailed insight into the metal-insulator transition of negative charge transfer compounds and should prove instructive for understanding metal-insulator transitions in other late transition metal compounds such as the nickelates.

Journal Keywords: Metal-insulator transition; Oxides; Strongly correlated systems

Subject Areas: Materials, Physics


Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: Advanced Light Source; Canadian Light Source