Effect of heat treatment in hydrogen on the phase formation processes in nanoscale FePt and FePtPd films and their Raman spectra

DOI: 10.62564/M4-TV1849

Mykola But¹, Daria Horodnycha¹, Ruslan Shkarban¹, Maksym Barabash^1,2, Tetiana Verbytska¹, Iurii Makogon<sup>1

1</sup>Educational and Research Institute of Materials Science and Welding National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
²Technical Center, N.A.S. of Ukraine


Nanoscale films based on FePt(Pd) layers with an ordered L1o structure have a promising application both for ultra-high-density magnetic information carriers and for future spintronics devices. The purpose of these studies was to determine the effect of the heat treatment in the hydrogen environment and the Pd addition on the phase composition and structure of the films and their optical properties. Equiatomic Fe50Pt50 and Fe50(Pt0.75Pd0.25)50 films with a total thickness of 15 nm were obtained by magnetron sputtering on a SiO2/Si(001) substrate at room temperature. After deposition, the films were annealed in a hydrogen environment at temperatures of 400 - 700 °С for 1 h. The processes of the A1 into L1o phase transformation were investigated by X-ray diffraction, RHEED method and Raman scattering spectroscopy. The ordered L1o phase in both films begins to form at 400 °C. As the temperature rises, its amount increases. The Pd addition activates the ordering process and contributes to increasing the ordering degree, the formation of (001)-textured grains up to a temperature of 650 °C, but does not affect the size of the FePt or FePtPd coherent scattering regions. It was found that after annealing to 700 °C, only the L1o phase is observed in both films. The change in the Raman spectra confirms the presence of embodied hydrogen in the films and а two-phase state (A1+L1o) in the films up to a temperature of 650 °C, inclusive. The variation in Raman spectra and the luminescence effect are manifested in different structural combinations of FePt and FePtPd films. The non-linear change in the intensity of the Raman spectra is the basis for the appearance of forced Raman scattering effects. Enhancement of luminescence by the film allows to identify the structural A1into L1o phase transformation dynamics.

Keywords
ordering, hydrogen, FePt, FePtPd, Raman spectra

Acknowledgments
The authors would like to thank Prof. M. Albrecht from Augsburg University (Germany) and workers for sample preparation, assistance in investigations and discussion of results . This work was financially supported by DAAD the Grant ID 57630758

References
[1] Levchuk L., Shkarban R., Kotenko I., Graivoronska K., Fesenko O., Lukianenko I., Verbytska T., Makogon Iu., Barabash M. Changes in Raman spectra upon formation of ordered L1o FePd phase during annealing in vacuum and in hydrogen atmosphere, Thin Solid Films. 2024. V. 789. 1402000. https://doi.org/10.1016/j.tsf.2024.140200