Speaker
Description
Fe-based nanocrystalline alloys exhibit distinctive soft magnetic properties, which are obtained through a heat treatment process. This treatment partially devitrifies the amorphous precursor, leading to the development of a microstructure composed of ultra-fine grains, smaller than $30$ nm, embedded within a remaining amorphous matrix [1]. The application of heat treatment combined with tensile deformation offers a promising method to further optimize microstructure, resulting in enhanced magnetic properties [2]. The induced magnetic anisotropy energy is directly proportional to the stress applied during annealing and can reach values in the range of several thousand J/m$^3$, two orders of magnitude greater than the typical field-induced anisotropies. These robust and precisely controlled anisotropies are particularly valuable for applications such as magnetic energy storage cores, which demand low permeability, typically around a few hundred. Previous research indicates that the stress-induced anisotropy (SIA) in Fe-based alloys stems from the structural anisotropy of Fe$_3$Si nanocrystalline grains [3,4].
This study builds upon previous research by providing direct in-situ X-ray diffraction (XRD) observations of SIA in nanocrystalline Fe-based alloy (Vitroperm $800$). Melt spun amorphous ribbons were subjected to tensile loading at elevated temperatures and temporal evolution of the SIA formation was observed using in-situ XRD experiments at the P$02.1$ beamline of the synchrotron storage ring PETRA III at DESY Hamburg. These studies demonstrate how tensile stress during annealing influences the lattice strain of cubic Fe$_3$Si phase, offering a more detailed understanding of the mechanisms driving SIA.
Acknowledgements
This research was supported by the Grant Programme for SAS PhD students, project no. APP0626, funded by the Slovak Academy of Sciences. Funded by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under the project No. 09I03-03-V03-00034.
References
[1] Y. Yoshizawa et al., “New Fe-based soft magnetic alloys composed of ultrafine grain structure,” Journal of Applied Physics, vol. 64, no. 10. AIP Publishing, pp. 6044–6046, Nov. 15, 1988. https://doi.org/10.1063/1.342149
[2] G. Herzer et al., “Magnetic properties of nanocrystalline FeCuNbSiB with huge creep induced anisotropy,” Journal of Physics: Conference Series, vol. 266. IOP Publishing, p. 012010, Jan. 01, 2011. https://doi.org/10.1088/1742-6596/266/1/012010
[3] M. Ohnuma et al., “Direct evidence for structural origin of stress-induced magnetic anisotropy in Fe–Si–B–Nb–Cu nanocrystalline alloys,” Applied Physics Letters, vol. 83, no. 14. AIP Publishing, pp. 2859–2861, Oct. 06, 2003. https://doi.org/10.1063/1.1615672
[4] D. Yudina et al., “Structural aspects of stress-induced magnetic anisotropy in Fe-based nanocrystalline alloy,” Journal of Alloys and Compounds, vol. 960. Elsevier BV, p. 171011, Oct. 2023. https://doi.org/10.1016/j.jallcom.2023.171011
