Perovskite oxyhydride EuVO₂H exhibits a Mott insulating state derived from V^IIIO₂ layers and a ferromagnetic state derived from Eu^IIH layers, with compressive strain inducing intersite charge transfer (ICT) in thin films, accompanied by an increased ferromagnetic transition temperature (T_C) and the emergence of perpendicular magnetic anisotropy (PMA). While ICT has previously been adjusted by film thickness (or substrate strain), this study demonstrates its control by Eu-site substitution with Sr. Utilizing topochemical hydride reduction, we fabricated Eu_1–xSr_xVO₂H solid solution thin films on SrTiO₃ substrates, providing −0.6% compressive strain. With an increasing Sr content, the Eu valence remains almost unchanged, indicating a reduced level of electron transfer from the Eu 4f band to the V 3d_xy band. This observation is ascribed to the reduced dispersion of the Eu 4f band, in contrast with our previous study on EuVO₂H in which the empty V 3d_xy bandwidth was manipulated by film thickness, manifesting the possibility of independent control over the d band and f band, an achievement unexplored in previous oxide research. Sr substitution not only decreases T_C but also suppresses PMA. In addition, the application of high pressure to Eu_0.9Sr_0.1VO₂H powder induces a continuous valence evolution of Eu, as opposed to that of pristine EuVO₂H, which undergoes a first-order valence transition. This study offers possibilities for independent control of the electronic structure of systems containing both transition metals and rare earth elements.

中文翻译：

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通过 Eu1–xSrxVO2H 氢氧化物薄膜中的 Eu 4f 能带工程进行位点间电荷转移

钙钛矿氢氧化合物EuVO _{2 H表现出源自V} ^III O ₂层的莫特绝缘态和源自Eu ^II H层的铁磁态，压缩应变诱导薄膜中的位点间电荷转移（ICT），并伴随着铁磁转变温度的升高（T _C）和垂直磁各向异性（PMA）的出现。虽然 ICT 之前是通过薄膜厚度（或基底应变）进行调整的，但本研究证明了它是通过用 Sr 取代 Eu 位点来控制的。利用拓扑化学氢化物还原，我们在 SrTiO 上制备了 Eu _{1– x} Sr _x VO ₂ H 固溶体薄膜_{3 个}基板，提供-0.6% 的压缩应变。随着Sr含量的增加，Eu价态几乎保持不变，表明从Eu 4f带到V 3d _xy带的电子转移水平降低。这一观察结果归因于Eu 4f带的色散减少，与我们之前对EuVO ₂ H的研究相反，其中空V 3d _xy带宽由薄膜厚度控制，表明独立控制d带和f带的可能性带，这是以前氧化物研究中尚未探索的成就。 Sr 取代不仅降低T _C而且抑制 PMA。此外，对Eu _0.9 Sr _0.1 VO ₂ H粉末施加高压会引起Eu的连续价态演化，这与经历一级价态跃迁的原始EuVO ₂ H相反。这项研究为独立控制包含过渡金属和稀土元素的系统的电子结构提供了可能性。