Polarized x-ray absorption spectra of La{sub 1-x}Sr{sub 1+x}MnO{sub 4}: Electronic state of Mn atoms

Journal Article · Mon Aug 15 04:00:00 EDT 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.72.085106· OSTI ID:20719350

Herrero-Martin, Javier; Garcia, Joaquin; Subias, Gloria; Blasco, Javier; Sanchez, Maria Concepcion ^[1]

---

1. Instituto de Ciencia de Materiales de Aragon, Departamento de Fisica de la Materia Condensada, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain)

We have measured polarized x-ray-absorption near-edge structure and extended x-ray-absorption fine structure spectra at the Mn K edge on La{sub 1-x}Sr{sub 1+x}MnO{sub 4} samples with x=0, 0.3, and 0.5 at different temperatures from 50 K up to 300 K. Both fluorescence and total electron yield modes were used for polarized measurements, whereas nonpolarized absorption spectra have also been recorded in transmission mode on powder samples for x=0, 0.3, 0.45, 0.5, and 0.55. The experiment discards the presence of distinct Mn{sup 3+}/Mn{sup 4+} integer valence states for any of the mixed-valence samples (x=0.3,0.5) in the whole temperature range. The local structure (geometrical and electronic) around the Mn atom is anisotropic in all samples. Moreover, there is no significant change in the Mn local geometric and electronic structure of compounds with 0.45{<=}x{<=}0.55 crossing the charge-ordering transition (T{sub CO}=230 K). The anisotropy in the absorption spectra is then explained in terms of the tetragonal distortion of the MnO{sub 6} octahedron. It decreases as x increases, the oxygen environment being nearly isotropic for La{sub 0.5}Sr{sub 1.5}MnO{sub 4}. Anisotropy is also observed at the prepeaks. The intensity of the in-plane structures strongly increases with the Sr content, indicating that the doped holes mainly go into the ab plane. We conclude that the electronic state of Mn atoms can be only described in terms of an intermediate valence, even for anisotropic samples such as two-dimensional La-Sr manganites.

• OSTI ID: 20719350
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 8 Vol. 72; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
ANISOTROPY
ATOMS
CRYSTAL STRUCTURE
DOPED MATERIALS
ELECTRONIC STRUCTURE
ELECTRONS
FINE STRUCTURE
FLUORESCENCE
HOLES
LANTHANUM COMPOUNDS
MANGANATES
MANGANESE IONS
OXYGEN
POWDERS
STRONTIUM COMPOUNDS
TEMPERATURE DEPENDENCE
VALENCE
X RADIATION
X-RAY SPECTRA
X-RAY SPECTROSCOPY