X-ray magnetic circular dichroism at the Fe L2,3, Ce M4,5 and Ce L2,3 absorption edges of CeFe2 are reported. Application of the sum rules yields both the magnitude and the direction of the magnetic contributions (Fe 3d, Ce 5d and Ce 4f ) to the total moment in CeFe2. A total Ce magnetic contribution of −0.29µB (M 5d = −0.13µB, M 4f = −0.16µB) and a ratio for the 4f contribution Lz / Sz ≈ −1 are found, which confirms that the 4f states are highly hybridised in CeFe2. These results are in good agreement with previously published LSDA calculations.
The absorption coefficients and the Faraday rotation spectra of nanocrystalline cobalt ferrite thin films were determined in the visible–near infrared range. The films prepared by rf sputtering in an Ar–O2 atmosphere display magnetic and structural properties which differ from those of the bulk material. Optical and magneto-optical transitions observed in the films are identified by comparing our spectra with those obtained with well characterized bulk materials. In the bulk, cations with an octahedral environment (point group 3̄m) locate on a center of symmetry and the corresponding optical transitions have a very small oscillator strength. In the films, these transitions may lead to a large absorption coefficient. One absorption band appears that cannot be identified on the basis of the symmetry properties of the bulk material. The observed absorption spectra may be explained, however, if some of the cations have one of the following symmetry point groups: 4, 422, and 32. The Faraday rotation spectra show that: (1) the magnetic disorder increases when the oxygen to argon ratio is increased, (2) the disorder influences the cations on both tetrahedral and octahedral sites of the spinel structure.
The nanocrystalline MnxFe3−xO4 (x=0, 1.18, 1.56, and 1.9) spinel ferrite thin films were investigated by means of the x-ray absorption spectroscopy and x-ray magnetic circular dichroism at the Mn and Fe L2,3 edges. The cationic distributions of thin spinel ferrite films for x=1.18 and 1.56 were determined using a crystal field atomic multiplets scheme for arbitrary symmetry. The results are compared with the distribution of cations obtained from the differential thermogravimetry analysis of fine powders of corresponding compositions.
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