MS16-P10 Determination of the crystal structures of an oxidized TbDy2Fe6 thin film by synchrotron radiation anomalous X-ray scattering Chih-Hao Lee (Department of Engineering and System Science, National Tsing Hua University , Hsinchu, Taiwan) Wen-Ching Chang (Department of Engineering and System Science, National Tsing Hua University , Hsinchu, Taiwan)email: chlee@mx.nthu.edu.twThe cubic Laves phase RFe2 compounds (R= Tb and Dy) with cubic MgCu2-type structure have giant room temperature magnetostriction constants. To make this compound as a thin film is very useful for the applications on Micro-Electro- Mechanical Systems However, as a thin film, it is apt to the oxidation of the thin film. To study the oxidation of RFe2 thin film is of interesting in the material science.
In this work, 160 nm TbDy2Fe6 thin films were prepared by magnetron sputtering and annealed in the range of temperature between 550 and 850 ℃. The structure of TbDy2Fe6 thin films were characterized by X-ray diffraction, and strong diffraction peaks of rare-earth oxides, Tb2O3 or Dy2O3 and other non-stoichiometric peaks were found.  Since the lattice structure of Tb2O3 is very similar to that of Dy2O3, the composition of Tb2O3 and Dy2O3 cannot be determined by XRD separately. By using synchrotron radiation anomalous X-ray scattering, the amount of Tb and/or Dy oxidized at different annealing temperatures was determined. In addition, a pure Fe peak (110) was also detected using XRD. We use the anomalous X-ray diffraction and electron probe micro-analyzer to study this Fe diffraction peak.
With the anomalous X-ray scattering, the composition of the Tb2O3 or Dy2O3 was found to be the same as the sputtering target materials. It might be due to the same formation energies of oxides of Tb and Dy. In addition, 600 nm Fe clusters phase segregated from the bulk matrix without oxidation was also identified. These pure Fe cluster without oxidation might be due to the protection effect of Gd and Tb matrix. 
In conclusion, oxidation of TbDy2Fe6 thin films were studied by X-ray anomalous scattering. The composition of Tb2O3 and Dy2O3 are similar to the composition of sputtering target. In addition, the Fe clusters phase segregated from the bulk matrix without oxidation was also identified.
 
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Keywords: TbDy2Fe6, oxidation, anomalous X-ray scattering