Crystal field and low energy excitations measured by high resolution RIXS at the L3 edge of Cu, Ni and Mn

Ghiringhelli, G.; Piazzalunga, A.; Wang, X.; Bendounan, Azzedine; Berger, H.; Bottegoni, Federico; Christensen, Niels Bech; Dallera, C.; Grioni, M.; Grivel, Jean‐Claude; Sala, M. Moretti; Patthey, L.; Schlappa, Justine; Schmitt, Thorsten; Strocov, Vladimir N.; Braicovich, L.

doi:10.1140/epjst/e2009-00993-8

Cited by 31 publications

(40 citation statements)

References 19 publications

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“…As further support to our interpretation of the RIXS spectra, we show an example of insulating LMO films, excited at the same energy as for the other cases: the spectrum is incompatible with dd excitations of Mn 2+ and is rather typical of Mn 3+ in magnanites 26 .…”

Section: Resonant Inelastic X-ray Spectroscopy Measurementssupporting

confidence: 85%

Multiple double-exchange mechanism byMn2+doping in manganite compounds

et al. 2010

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Double-exchange mechanisms in RE1−xAExMnO3 manganites (where RE is a trivalent rare-earth ion and AE is a divalent alkali-earth ion) relies on the strong exchange interaction between two Mn 3+ and Mn 4+ ions through interfiling oxygen 2p states. Nevertheless, the role of RE and AE ions has ever been considered "silent" with respect to the DE conducting mechanisms. Here we show that a new path for DE-mechanism is indeed possible by partially replacing the RE-AE elements by Mn 2+ -ions, in La-deficient LaxMnO 3−δ thin films. X-ray absorption spectroscopy demonstrated the relevant presence of Mn 2+ ions, which is unambiguously proved to be substituted at La-site by Resonant Inelastic X-ray Scattering. Mn 2+ is proved to be directly correlated to the enhanced magnetotransport properties because of an additional hopping mechanism trough interfiling Mn 2+ -ions. Such a scenario has been theoretically confirmed by calculations within the effective single band model. The use of Mn 2+ both as a doping element and an ions electronically involved in the conduction mechanism reveals a new phenomena in transport properties of manganites. More important, such a strategy might be also pursed in other strongly correlated materials.

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Section: Resonant Inelastic X-ray Spectroscopy Measurementssupporting

confidence: 85%

Multiple double-exchange mechanism byMn2+doping in manganite compounds

et al. 2010

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“…In principle, d → d excitations provide a testing ground for the validity of conventional Raman selection rules within RIXS, and such excitations have been well studied with soft X-ray RIXS at the Cu L- [8][9][10]40,41 and M-edges, 11 with optical absorption, 42 with large-shift Raman scattering, 43 and with different theoretical methods. 44,45 Although for Nd 2 CuO 4 only the A 2g (d x 2 −y 2 → d xy ) Cu crystal-field excitation has been observed around 1.4 eV, 43 the crystal-field excitations of tetragonal Sr 2 CuO 2 Cl 2 have been extensively studied 10,11,42,44 and their energies should be similar to those of Nd 2 CuO 4 .…”

Section: Discussionmentioning

confidence: 99%

Polarization dependence and symmetry analysis in indirectK-edge RIXS

et al. 2010

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We present a study of the charge-transfer excitations in undoped Nd 2 CuO 4 using resonant inelastic X-ray scattering (RIXS) at the Cu K-edge. At the Brillouin zone center, azimuthal scans that rotate the incidentphoton polarization within the CuO 2 planes reveal weak fourfold oscillations. A comparison of spectra taken in different Brillouin zones reveals a spectral weight decrease at high energy loss from forward-to back-scattering. We show that these are scattered-photon polarization effects related to the properties of the observed electronic excitations. Each of the two effects constitutes about 10% of the inelastic signal while the '4p-as-spectator' approximation describes the remaining 80%. Raman selection rules can accurately model our data, and we conclude that the observed polarization-dependent RIXS features correspond to E g and B 1g charge-transfer excitations to non-bonding oxygen 2p bands, above 2.5 eV energy-loss, and to an E g d → d excitation at 1.65 eV.Raman scattering and optical spectroscopy have enabled tremendous contributions to the study of condensed matter systems. Both probes use ∼ 1 eV light and are limited to essentially zero momentum transfer. In order to investigate the charge response of a material throughout the Brillouin zone, photons in the X-ray regime must be used. X-ray Raman scattering, more commonly referred to as resonant inelastic X-ray scattering (RIXS), allows the measurement of the momentum dependence of charge excitations. Even though it has successfully been used to study the physics of a wide array of systems, 1-5 this resonant technique is relatively new and there is still much to learn about the details of its cross section.One of the strengths of conventional Raman scattering derives from the fact that the technique allows the determination of the symmetry of excitations by selecting the polarization of the incident and scattered photons. Only polarization dependent soft (or direct 6 ) X-ray RIXS studies, at the O K-edge or the Cu L-and M-edges of the cuprates, 7-11 have shown that photon polarization can be used to select different electronic excitations. In these cases, the photon polarization effects are understood to come from the direct interaction of the photoelectron, excited into the valence system, with the valence electrons. This is why this type of RIXS is commonly referred to as direct. 6 On the other hand, tuning the incident energy to the Cu K-edge excites the photoelectron into the Cu 4p band approximately 10-20 eV above the 3d valence levels. The relatively large separation in energy from the valence levels as well as the large spatial extent of the 4p orbital are believed to prevent the photoelectron from interacting with the valence system, and this type of RIXS is in turn referred to as indirect. 6 Accordingly, theoretical models of this type of RIXS accordingly do not include possible interactions of the 4p photoelectron with the valence system, 12-15 which is commonly referred to as the '4p-as-spectator' approximation.RIXS investigations of ...

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“…RIXS at the L-edge in LaMnO 3 was reported by Ghiringhelli et al 157) While the spectrum of MnO is dominated by sharp d-d excitations, charge transfer excitations are observed with a comparable intensity to the d-d excitations in LaMnO 3 . This suggests that the screening of the core hole potential is relatively prominent in the RIXS process of LaMnO 3 .…”

Section: )mentioning

confidence: 68%

Inelastic X-ray Scattering Studies of Electronic Excitations

2013

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Inelastic x-ray scattering (IXS) has developed into one of the most powerful momentum-resolved spectroscopies. Especially in the last decade, it has achieved significant progress utilizing brilliant x-rays from third-generation synchrotron radiation facilities. Simultaneously, theoretical efforts have been made to predict or interpret the experimental spectra. One of the scientific fields studied intensively by IXS is strongly correlated electron systems, where the interplay of charge, spin, and orbital degrees of freedom determines their physical properties. IXS can provide a new insight into the electron dynamics of the systems through the observation of charge, spin, and orbital excitations. Focusing on the momentum-resolved electronic excitations in strongly correlated electron systems, we review IXS studies and the present capabilities of IXS for the study of the dynamics of materials. With nonresonant inelastic x-ray scattering (NIXS), one can directly obtain dynamical charge correlation and we discuss its complementary aspects with inelastic neutron scattering. NIXS also has a unique capability of measuring higher multipole transitions, which are usually forbidden in conventional optical absorption. Resonant inelastic x-ray scattering (RIXS) is now established as a valuable tool for measuring charge, spin, and orbital excitations in a momentum-resolved manner. We describe RIXS works on cuprates in detail and show what kind of electronic excitations have been observed. We also discuss RIXS studies on other transition-metal compounds. Finally, we conclude with an outlook on IXS using next-generation x-ray sources.

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Crystal field and low energy excitations measured by high resolution RIXS at the L3 edge of Cu, Ni and Mn

Cited by 31 publications

References 19 publications

Multiple double-exchange mechanism byMn2+doping in manganite compounds

Multiple double-exchange mechanism byMn2+doping in manganite compounds

Polarization dependence and symmetry analysis in indirectK-edge RIXS

Inelastic X-ray Scattering Studies of Electronic Excitations

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