Surface physics, thin films

Study of structural and magnetic properties of epitaxial thin-film nanostructures enriched with $^{57}$Fe during thermal oxidation

I. V. Blinov, M. A. Milyaev, Yu. V. Korkh, T. V. Kuznetsova, I. K. Maksimova, A. V. Stolbovsky, A. Yu. Germov, B. Yu. Goloborodskii, R. M. Farakhutdinov, E. V. Osinnikov, D. I. Devyaterikov

Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg

Abstract: This work investigates the effects of thermomagnetic treatment on the structural and magnetic properties of epitaxial layered structures MgO(100)/$^{57}$Fe(50 nm)/Cr(2 nm). Using X-ray diffraction, Raman spectroscopy, atomic force microscopy, and Mössbauer spectroscopy, we analyzed structural changes during annealing in the temperature range of 200–300$^\circ$C. The study reveals that at temperatures above 250$^\circ$C, oxygen diffusion through the protective Cr layer leads to the formation of antiferromagnetic $\alpha$-Fe$_2$O$_3$. An increase in coercivity up to 190 Oe at 280$^\circ$C is attributed to exchange coupling between Fe and $\alpha$-Fe$_2$O$_3$. However, no shift in the magnetic hysteresis loop (exchange bias) is observed, which may result from low magnetic anisotropy of hematite ($\alpha$-Fe$_2$O$_3$) and structural and chemical inhomogeneity at the interlayer boundaries.

Keywords: hematite, unidirectional anisotropy, thermomagnetic treatment, oxygen diffusion.

Received: 14.05.2025
Revised: 30.05.2025
Accepted: 04.06.2025

DOI: 10.61011/FTT.2025.06.60948.120-25

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