The Influence of Surface Terminal Layer and Surface Defects on the Electronic Structure of CMR Perovskites: La_0.65A_0.35MnO₃ (A = Ca, Sr, Ba)

Authors

Jaewu Choi, University of Nebraska-LincolnFollow
Hani Dulli, University of Nebraska-LincolnFollow
Sy-Hwang Liou, University of Nebraska-LincolnFollow
Peter A. Dowben, University of Nebraska-LincolnFollow
Marjorie Langell, University of Nebraska-LincolnFollow

Date of this Version

4-27-1999

Comments

Published in physica status solidi (b) 214 (1999), pp. 45–57. Copyright © 1999 John Wiley & Sons Co. Used by permission. http://www3.interscience.wiley.com/cgi-bin/jhome/40001185

Abstract

The electronic structure near to the Fermi level of the colossal magnetoresistance (CMR) perovskite manganite materials, La_0.65A_0.35MnO₃ (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_0.65A_0.35MnO₃ and La_0.65A_0.35MnO₃ while there is a gap, about 1.5 eV, for La_0.65A_0.35MnO₃. There is a shift to higher binding energies of the extensively hybridized Mn–O Δ₅ (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_0.65A_0.35MnO₃, La_0.65A_0.35MnO₃, and La_0.65A_0.35MnO₃, respectively. The O–Mn–O terminal layer in these materials seems to be much more defect free than is the case for La_0.65A_0.35MnO₃, where the Ca–O terminal layer appears to be rich in defects.