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arXiv · 2302.02322

Origin of magnetically dead layers in spinel ferrites $M\text{Fe}_2\text{O}_4$ grown on $\text{Al}_2\text{O}_3$: Effects of post-deposition annealing studied by XMCD

Yosuke Nonaka·Yuki K. Wakabayashi·Goro Shibata·Shoya Sakamoto·Keisuke Ikeda·Zhendong Chi·Yuxuan Wan·Masahiro Suzuki·Arata Tanaka·Masaaki Tanaka·Atsushi Fujimori
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Abstract

We study the electronic and magnetic states of as-grown and annealed $M\text{Fe}_2\text{O}_4$(111)/$\text{Al}_2\text{O}_3$(111) ($M=\text{Co, Ni}$) thin films with various thicknesses grown on Si(111) substrates with the $\gamma$-$\text{Al}_2\text{O}_3$(111) buffer layers by using x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), to investigate magnetically dead layers in these films. Although the magnetically dead layers in the as-grown samples are formed near the interface with the $\text{Al}_2\text{O}_3$ buffer layer, we reveal that ferrimagnetic order is partially recovered by post-deposition annealing at 973 K for 48 hours in air. By analyzing the line shapes of the XAS and XMCD spectra, we conclude that, in the dead layers, there are a significant number of vacancies at the $T_d$ sites of the spinel structure, which may be the microscopic origin of the degraded ferrimagnetic order in the $M\text{Fe}_2\text{O}_4$(111) thin films.

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Yosuke Nonaka, Yuki K. Wakabayashi, Goro Shibata, Shoya Sakamoto, Keisuke Ikeda, Zhendong Chi, Yuxuan Wan, Masahiro Suzuki, Arata Tanaka, Masaaki Tanaka, Atsushi Fujimori. 2023-02-05. Origin of magnetically dead layers in spinel ferrites $M\text{Fe}_2\text{O}_4$ grown on $\text{Al}_2\text{O}_3$: Effects of post-deposition annealing studied by XMCD. https://doi.org/10.1103/physrevmaterials.7.044413

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