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The Influence of Surface Terminal Layer and Surface Defects on the Electronic Structure of CMR Perovskites: La 0.65 A 0.35 MnO 3 (A = Ca, Sr, Ba)
Author(s) -
Choi Jaewu,
Dulli Hani,
Liou S.H.,
Dowben P. A.,
Langell M. A.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199907)214:1<45::aid-pssb45>3.0.co;2-#
Subject(s) - materials science , layer (electronics) , terminal (telecommunication) , surface (topology) , surface layer , crystallography , mineralogy , condensed matter physics , chemistry , nanotechnology , physics , geometry , engineering , telecommunications , mathematics
The electronic structure near to the Fermi level of the colossal magnetoresistance (CMR) perovskite manganite materials, La 0.65 A 0.35 MnO 3 (A = Ca, Sr, Ba), has been studied using both photoemission and inverse photoemission spectroscopy. The electronic structure for all three materials is very similar and consistent with an Mn–O terminal layer regardless of dopant. Small differences in the electronic structure among the materials are, however, observed. The observed band gap is not significant for La 0.65 Ca 0.35 MnO 3 and La 0.65 Ba 0.35 MnO 3 while there is a gap, about 1.5 eV, for La 0.65 Sr 0.35 MnO 3 . There is a shift to higher binding energies of the extensively hybridized Mn–O Δ 5 (e) bands for the surface (the surface on the Mn–O plane with C 4v symmetry) and t 2g bands for the bulk in the valence band spectra with increasing atomic number or atomic radius of dopants, approximately to 5.8, 6.8, and 7.8 eV for La 0.65 Ca 0.35 MnO 3 , La 0.65 Sr 0.35 MnO 3 , and La 0.65 Ba 0.35 MnO 3 , respectively. The O–Mn–O terminal layer in these materials seems to be much more defect free than is the case for La 0.9 Ca 0.1 MnO 3 , where the Ca–O terminal layer appears to be rich in defects.