title: Resonant photoemission from complex cuprates and nickelates.
abstract: 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 Nd(2)Ni(1 - x)Cu(x)O(4), La(2 - x)Sr(x)Ni(1- y)Fe(y)O(4 + delta) and Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta). 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 La(2 - x)Sr(x)Ni(1 - y)Fe(y)O(4 + delta), this approach is used to infer a valence state of >/= 3.0 for Fe. In the case of Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta), 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.
authors.forename: W R
authors.initials: WR
authors.lastname: Flavell
authors.forename: J
authors.initials: J
authors.lastname: Hollingworth
authors.forename: J F
authors.initials: JF
authors.lastname: Howlett
authors.forename: A G
authors.initials: AG
authors.lastname: Thomas
authors.forename: M M
authors.initials: MM
authors.lastname: Sarker
authors.forename: S
authors.initials: S
authors.lastname: Squire
authors.forename: Z
authors.initials: Z
authors.lastname: Hashim
authors.forename: M
authors.initials: M
authors.lastname: Mian
authors.forename: P L
authors.initials: PL
authors.lastname: Wincott
authors.forename: D
authors.initials: D
authors.lastname: Teehan
authors.forename: S
authors.initials: S
authors.lastname: Downes
authors.forename: F E
authors.initials: FE
authors.lastname: Hancock