EFFECT OF THE ANNEALING TEMPERATURE ON THE ELECTRONIC AND ATOMIC STRUCTURES OF EXCHANGE-BIASED NiFe–FeMn BILAYERS

Abstract

In this study we measured the Fe, Mn, and Ni L2,3-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 L2,3-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.