Anomalous local lattice disorder and distortion in A2Mo2O7 pyrochlores

JOURNAL OF ALLOYS AND COMPOUNDS

卷:723

Article

Castellano, C.¹  Berti, G.^2,9  Rubio-Marcos, F.³  Lamura, G.⁴  Sanna, S.⁵  Salas-Colera, E.^6,7  Brambilla, A.²  Munoz-Noval, A.⁸  Duo, L.²  Demartin, F.¹ 

[1] Univ Milan, Dipartimento Chim, Via Golgi 19, I-20133 Milan, Italy

[2] Politecn Milan, Dipartimento Fis, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy

[3] CSIC, Electroceram Dept, Inst Ceram & Vidrio, Kelsen 5, Madrid 28049, Spain

[4] CNR SPIN, Corso Perrone 24, I-16146 Genoa, Italy

[5] Univ Bologna, Dept Phys & Astron, I-40127 Bologna, Italy

[6] CSIC, ICMM, Sor Juana Ines de la Cruz 3, Madrid 28049, Spain

[7] Spanish CRG BM25 SpLine, ESRF 71 Ave Martyrs CS 40220, FR-38043 Grenoble, France

[8] Hiroshima Univ, Dept Appl Chem, 1-4-1 Kagamiyama, Hiroshima 7398527, Japan

[9] Max Planck Gesell, Fritz Haber Inst, Dept Chem Phys, Faradayweg 4-6, D-14195 Berlin, Germany

关键词: Oxide materials;    Pyrochlores;    order-disorder effects;    EXAFS;   

DOI  :  10.1016/j.jallcom.2017.06.272

来源: Elsevier

【 摘 要 】

We present an extended X-ray absorption fine structure study of the pyrochlores A(2)Mo(2)O(7) (A = Gd, Dy, Ho, Er), as a function of temperature. While in the three spin-glass compositions Dy2Mo2O7, Ho2Mo2O7 and Er2Mo2O7 the Debye temperatures are in accordance with other pyrochlores and the static disorder contributions are compatible with a lattice frustration, in the low-temperature-ferromagnetic Gd2Mo2O7 system we point out an anomalous enhancement of the local structure disorder below about 225 K down to low temperatures. Moreover, considering the general pyrochlore predisposition towards structural disorder, we prove the presence on a local scale of at least a bimodal distribution of the Mo-O(1) octahedral interatomic distances for all the studied compounds, consisting of two shorter and four longer bond lengths. Our results suggest that the local structure order parameter plays an important role in the ferromagnetic or spin-glass phase stabilization. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

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