Using epitaxial stabilization, we synthesized single-phase (001)-oriented thin films of DyFe₂O_4+x on (111) MgAl₂O₄ substrates by molecular-beam epitaxy. The metastable DyFe₂O₄ polymorph formed is isostructural to known trigonal ferrimagnetic RFe₂O₄ phases with space group $R\bar{3}m$, where R = Ho to Lu. The epitaxial DyFe₂O₄ thin films have two in-plane orientation relationships: [100] DyFe₂O₄ || $\left[2\overline{11}\right]$ MgAl₂O₄ plus a twin variant related by a 60° in-plane rotation. DyFe₂O₄ is not bulk stable and has never been synthesized before. Indeed, it has been predicted to be on the edge energetically of what may be possible to stabilize. The fact that the RFe₂O₄ phase is stable for all elements leading up to dysprosium (Ho–Lu) leads us to believe that DyFe₂O₄ could be a “remnant metastable phase,” one which, given the right thermodynamic conditions, could become the lowest free energy phase. We find that although we are able to get structurally very close to $R\bar{3}m$ DyFe₂O₄, the films are not stoichiometric as they have an increased c lattice parameter, indicative of extra oxygen as is sometimes seen in other RFe₂O₄ phases. The unintended surplus oxygen opens questions regarding what may be achievable using such tricks as epitaxial stabilization to access metastable phases and whether this indeed constitutes “remnant metastability.”

中文翻译：

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DyFe2O4：分子束外延生长的新型三角稀土铁氧体

使用外延稳定，我们通过分子束外延在（111）MgAl ₂ O ₄衬底上合成了单相（001）取向的DyFe ₂ O _{4 + x}薄膜。形成的亚稳态DyFe ₂ O ₄多晶型与具有空间群的已知三角亚铁磁R Fe ₂ O _4相同构$\mathrm{[R}\bar{3}米$，其中R = Ho到Lu。外延DyFe ₂ O ₄薄膜具有两个面内取向关系：[100] DyFe ₂ O ₄ ||$\left[\mathrm{2个}\overline{11}\right]$MgAl ₂ O ₄加上一个孪生变体，与面内旋转60°有关。DyFe ₂ O ₄不稳定，并且以前从未合成过。实际上，已经预料到它可能在能量上处于稳定的边缘。该事实[R的Fe ₂ Ø ₄阶段是领导到镝所有元素稳定（何璐）使我们相信，DyFe ₂ Ø ₄可能是一个“残亚稳相，”其中之一，给予正确的热力学条件，可能成为最低的自由能阶段。我们发现，尽管我们能够在结构上非常接近$\mathrm{[R}\bar{3}米$DyFe ₂ O ₄薄膜不是化学计量的，因为它们具有增加的c晶格参数，这表明有时在其他R Fe ₂ O ₄相中会看到额外的氧气。意外的多余氧气引起了人们的疑问，即使用外延稳定等手段进入亚稳相可以达到什么目的，以及这是否确实构成了“残余亚稳”。