Coexistence of site- and bond-centered electron localization in the high-pressure phase of LuFe sub(2) O sub(4)

• Published in: Physical review. B 2016-03, Vol.93 (10)
• Main Authors: Hearne, G R, Carleschi, E, Sibanda, W N, Musyimi, P, Diguet, G, Kudasov, Yu B, Maslov, D A, Korshunov, A S
• Format: Article
• Language: English
• Subjects: Bonding; Charge; Condensed matter; Iron; Localization; Networks; Position (location); Spectra
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.93.105101

components are obtained from in situ super(57) Fe Mossbauer spectroscopy pressure studies of the mixed-valence LuFe sub(2) O sub(4) multiferroic, up to 30GPa and on recovered high-pressure phase samples. Temperature-dependent Mossbauer spectra of the low-pressure phase show that Fe super(2+) and Fe super(3+) sites are discernible, consistent with known site-centered charge order in the triangular (frustrated) Fe sublattice network. Magnetic spectra of the high-pressure phase, stabilized in a rectangular Fe sublattice network at P> 8 GPa, exhibit fingerprints of iron in an intermediate valence state only. Temperature-dependent resistivity pressure studies evidence thermally activated small polaron motion in the high-pressure phase. These experimental signatures, complemented by ab initio calculations of electronic structure, are considered evidence of asymmetric dimer formation Fe super((2+[Delta]+)) Fe super((3-[Delta])+), where the minority-spin electron deconfinement coefficient is [Delta] = 0.3-0.4. Bragg satellites discerned in electron diffraction patterns of the metastable high-pressure phase possibly stem from this admixture of site- and bond-centered localization (intermediate-state charge order) in a magnetic background. This breaks inversion symmetry and potentially renders LuFe sub(2) O sub(4) in its high-pressure phase as a new charge order instigated (electronic) ferroelectric.