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In this study we measured the Fe, Mn, and Ni L[sub 2,3]-edge X-ray absorption near-edge structure (XANES) and K-edge extended X-ray absorption fine structure (EXAFS) of the ferromagnetic (FM) NiFe and antiferromagnetic (AFM) FeMn bilayer films prepared with various annealing temperatures. The branching ratios of the white-line intensities in the Fe, Mn, and Ni L[sub 2,3]-edges XANES spectra and consequently the magnetic properties of these exchange-biased FM NiFe — AFM FeMn bilayers are found to depend strongly on the annealing temperature. We find that the first peak in the Fe, Mn, and Ni K-edge EXAFS Fourier transform spectra are very similar, which suggests that the nearest-neighbor bond lengths among Fe, Mn, and Ni atoms are essentially the same in the NiFe-FeMn bilayers. However, the peaks at distances greater than ∼ 3 Å appear to be sensitive to the annealing temperature especially for the Fe and Mn K-edge spectra, which suggests that annealing alters the atomic structures of the next-nearest-neighbor and more distant shells surrounding the Fe and Mn atoms in the NiFe-FeMn bilayers. [ABSTRACT FROM AUTHOR]

Electronic structures of hole-doped and electron hole-doped manganites, La[sub 0.7]Ca[sub 0.3]MnO[sub 3] and La[sub 0.7]Ce[sub 0.3]MnO[sub 3], have been elucidated by X-ray absorption near-edge structure (XANES) spectra of O K- and Mn L[sub 3,2]-edges. In the electron-doped system, La[sub 0.7]Ce[sub 0.3]MnO[sub 3], the spectral features of O K-edge spectra are shifted by ∼ 1 eV towards the higher energy side and reduction of Mn valency from 4[sup +] and 3[sup +] to 3[sup +] and 2[sup +] is expected when compared to hole-doped manganite. The XANES of Ce M[sub 5,4]-edges indicates a tetravalent state for Ce, similar to that in CeO[sub 2]. Ce[sup 4+] is incorporated into the lattice of LaMnO[sub 3], resulting in the modification of MnO[sub 6] octahedra and also indicating strong hybridization of Ce 5d and/or Ce 4f states with O 2p states. [ABSTRACT FROM AUTHOR]