Huyan Shuyuan, Ryan Dominic H, Slade Tyler J, Lavina Barbara, Jose Greeshma, Wang Haozhe, Wilde John M, Ribeiro Raquel A, Zhao Jiyong, Xie Weiwei, Bi Wenli, Alp Esen E, Bud'ko Sergey L, Canfield Paul C
Ames National Laboratory, US DOE, Iowa State University, Ames, IA 50011.
Department of Physics and Astronomy, Iowa State University, Ames, IA 50011.
Proc Natl Acad Sci U S A. 2023 Dec 26;120(52):e2310779120. doi: 10.1073/pnas.2310779120. Epub 2023 Dec 19.
We present a comprehensive study of the inhomogeneous mixed-valence compound, EuPdS, by electrical transport, X-ray diffraction, time-domain Eu synchrotron Mössbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. Electrical transport measurements show that the antiferromagnetic ordering temperature, , increases rapidly from 2.8 K at ambient pressure to 23.5 K at 19 GPa and plateaus between ~19 and ~29 GPa after which no anomaly associated with is detected. A pressure-induced first-order structural transition from cubic to tetragonal is observed, with a rather broad coexistence region (20 GPa to ~30 GPa) that corresponds to the plateau. Mössbauer spectroscopy measurements show a clear valence transition from approximately 50:50 Eu:Eu to fully Eu at ~28 GPa, consistent with the vanishing of the magnetic order at the same pressure. X-ray absorption data show a transition to a fully trivalent state at a similar pressure. Our results show that pressure first greatly enhances , most likely via enhanced hybridization between the Eu 4 states and the conduction band, and then, second, causes a structural phase transition that coincides with the conversion of the europium to a fully trivalent state.
我们通过高压下的电输运、X射线衍射、时域铕同步辐射穆斯堡尔光谱和X射线吸收光谱测量，对非均匀混合价化合物EuPdS进行了全面研究。电输运测量表明，反铁磁有序温度(T_N)从常压下的2.8 K迅速增加到约19 GPa时的23.5 K，并在约19至约29 GPa之间保持平稳，此后未检测到与(T_N)相关的异常。观察到压力诱导的从立方到四方的一级结构转变，存在一个相当宽的共存区域（约20 GPa至约30 GPa），该区域对应于(T_N)的平稳阶段。穆斯堡尔光谱测量表明，在约28 GPa时，铕的价态从约50:50的Eu²⁺:Eu³⁺明显转变为完全的Eu³⁺，这与相同压力下磁有序的消失一致。X射线吸收数据表明在类似压力下转变为完全三价态。我们的结果表明，压力首先极大地提高了(T_N)，最有可能是通过增强Eu 4f态与导带之间的杂化作用，其次导致了结构相变，该相变与铕转变为完全三价态相吻合。
