Modeling hyperfine parameters observed from the charge-ordered to valence-mixed state of NdBaFe2O5

• Published in: Journal of physics. Condensed matter Vol. 24; no. 37; p. 376002
• Main Authors: Lindén, J, Karen, P
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 19.09.2012; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Mössbauer effect; other γ-ray spectroscopy; Physics; Electric field gradients; Hyperfine magnetic field; Moessbauer effect; Point charge approximation; Charge ordering; Barium Iron Neodymium Oxides Mixed; Isomer shift; Minority carriers; Energy level population; Mixed valence; Internal magnetic fields
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/24/37/376002

Orbital populations of the minority-spin Fe2+ electron in NdBaFe2O5 are extracted from electric and magnetic hyperfine parameters of 57Fe Mössbauer spectra across the temperature interval where charge ordering of the valence state 2.5 + of iron occurs. The previously used approach that assigns the minority-spin population to a single lowest-energy d orbital is expanded to three orbitals by setting up a system of equations in terms of the Fe2+/Fe3+ balance from isomer shift, a point-charge model for the valence and ligand contributions to the electric-field gradient, a point-dipole model for the dipolar contribution and an iterative scheme for small orbital contributions to the internal magnetic field. This allows us to model the hyperfine fields (electric and magnetic) in the intermediate temperature range of partial charge ordering between TV 210 K and Tp 285 K, for which the one-orbital model was insufficient.