We present an extended X-ray absorption fine structure study of the pyrochlores A2Mo2O7 (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.
Anomalous local lattice disorder and distortion in A2Mo2O7 pyrochlores / C. Castellano, G. Berti, F. Rubio Marcos, G. Lamura, S. Sanna, E. Salas Colera, A. Brambilla, A. Munoz-Noval, L. Duò, F. Demartin. - In: JOURNAL OF ALLOYS AND COMPOUNDS. - ISSN 0925-8388. - 723(2017 Nov), pp. 327-332.
Titolo: | Anomalous local lattice disorder and distortion in A2Mo2O7 pyrochlores |
Autori: | |
Parole Chiave: | Oxide materials; Pyrochlores; order-disorder effects; EXAFS |
Settore Scientifico Disciplinare: | Settore CHIM/03 - Chimica Generale e Inorganica Settore FIS/03 - Fisica della Materia |
Data di pubblicazione: | nov-2017 |
Rivista: | |
Tipologia: | Article (author) |
Data ahead of print / Data di stampa: | giu-2017 |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1016/j.jallcom.2017.06.272 |
Appare nelle tipologie: | 01 - Articolo su periodico |
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