Role of Oxygen Electrons in the Metal-Insulator Transition in the Magnetoresistive Oxide La${}_{2-2x}$Sr${}_{1+2x}$Mn${}_2$O${}_7$ Probed by Compton Scattering

Abstract

We have studied the [100]-[110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e. the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of the metal-insulator transition are identified in the momentum density for the paramagnetic phase above the Curie temperature. We interpret our results as providing direct evidence for the transition from the metallic-like to the admixed ionic-covalent bonding accompanying the magnetic transition. The number of electrons involved in this phase transition is estimated from the area enclosed by the Compton profile anisotropy differences. Our study demonstrates the sensitivity of the Compton scattering technique for identifying the number and type of electrons involved in the metal-insulator transition.

4 pages, 4 figures, accepted for publication in Physical Review Letters

References in corpus (3)

• Half-metallic ferromagnets: From band structure to many-body effects
• Spin moment over 10-300 K and delocalization of magnetic electrons above the Verwey transition in magnetite
• Orbital mixing and nesting in the bilayer manganites La${}_{2-2x}$Sr${}_{1+2x}$Mn${}_2$O${}_7$

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• Renormalization of f-levels away from the Fermi energy in electron excitation spectroscopies: Density functional results of Nd${}_{2-x}$Ce${}_x$CuO${}_4$
• Bulk Fermi surface and momentum density in heavily doped La${}_{2-x}$Sr${}_x$CuO${}_4$ using high resolution Compton scattering and positron annihilation spectroscopies
• A Minimal tight-binding model for ferromagnetic canted bilayer manganites
• Probing the semiconductor-to-dirac semimetal transition in Na-Sb-Bi alloys with x-ray Compton scattering