ISSN:
1600-5775
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
Synchrotron-excited resonant-photoemission measurements at rare-earth 4d → 4f and transition-metal 3p → 3d thresholds have been carried out using a variety of complex cuprates and nickelates on stations 6.1 (grazing-incidence monochromator) and 6.2 (toroidal-grating monochromator) at the SRS CLRC Daresbury Laboratory. The systems studied are Nd2Ni1 − xCuxO4, La2 − xSrxNi1− yFeyO4 + δ and Bi2Sr2Ca1 − xYxCu2O8 + δ. A combination of EDC and constant-initial-state data is used to examine the 4f and 3d contributions to the valence-band density of states and their binding-energy positions relative to the Fermi energy. This allows the study of the valence states of the transition-metal ions and their modulation on doping. For La2 − xSrxNi1 − yFeyO4 + δ, this approach is used to infer a valence state of ≥ 3.0 for Fe. In the case of Bi2Sr2Ca1 − xYxCu2O8 + δ, the effect of Cu valence modulation on the 3p resonance is observed as x is varied. This is discussed in the light of controversy surrounding shifts in core-level photoemission with doping for this system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0909049595008156
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