Experiments are reported, which allow us to quantify the near-surface cation diffusion in (001) oriented ${\mathrm{Fe}}_3{\mathrm{O}}_4$ single crystals at temperatures between 470 and 770 K. Thin homoepitaxial films of magnetite, grown using isotopically labeled ${}^{57}\mathrm{Fe}$, were investigated by neutron reflectivity and time-of-flight secondary ion mass spectrometry. By heating the thin films in high vacuum to different temperatures for a well-defined time and determining the ${}^{57}\mathrm{Fe}$ distribution along the surface normal, the diffusion lengths are obtained. For the investigated temperature range, diffusion constants of the order of ${10}^{-20}$ ${\mathrm{m}}^2$/s are deduced. These results are important in view of near-surface mass transport induced by oxygen chemical potential differences occurring when magnetite is exposed to different gas atmospheres or by adsorbates.

中文翻译：

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470 K下磁铁矿近表面区域铁扩散的观察

报告了实验，这使我们能够量化（001）取向的近表面阳离子扩散 ${铁}_3{\mathrm{Ø}}_4$ 温度在470至770 K之间的单晶。使用同位素标记生长的磁铁矿同质外延薄膜 ${}^{57}铁$通过中子反射率和飞行时间二次离子质谱分析。通过在高真空下将薄膜加热到不同的温度并持续规定的时间，然后确定${}^{57}铁$沿着表面法线分布，获得扩散长度。对于研究的温度范围，扩散常数约为${10}^{-20}$ ${\mathrm{米}}^2$/ s被推导。考虑到当磁铁矿暴露于不同的气体气氛中或被吸附物产生的氧化学势差引起的近地表质量传输，这些结果很重要。