Open AccessResonant Photoemission from Complex Cuprates and Nickelates
Author(s) -
Flavell W. R.,
Hollingworth J.,
Howlett J. F.,
Thomas A. G.,
Sarker Md. M.,
Squire S.,
Hashim Z.,
Mian M.,
Wincott P. L.,
Teehan D.,
Downes S.,
Hancock F. E.
Publication year - 1995
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049595008156
Subject(s) - angle resolved photoemission spectroscopy , cuprate , monochromator , valence (chemistry) , excited state , atomic physics , doping , condensed matter physics , fermi level , chemistry , inverse photoemission spectroscopy , physics , electronic structure , optoelectronics , wavelength , organic chemistry , quantum mechanics , electron
Synchrotron‐excited resonant‐photoemission measurements at rare‐earth 4 d → 4 f and transition‐metal 3 p → 3 d 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 + δ and Bi 2 Sr 2 Ca 1 − x Y x Cu 2 O 8 + δ . A combination of EDC and constant‐initial‐state data is used to examine the 4 f and 3 d 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 + δ , 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 + δ , the effect of Cu valence modulation on the 3 p 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.