Vacancy defects and monopole dynamics in oxygen-deficient pyrochlores. / Sala, Gabriele; Gutmann, Matthias; Prabhakaran, D.; Pomaranski, D.; Mitchelitis, C. ; Kycia, J.B.; Porter, Dan; Castelnovo, Claudio; Goff, Jon.

In: Nature Materials, Vol. 13, 05.2014, p. 488-493.

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Abstract

The idea of magnetic monopoles in spin ice has enjoyed much success at intermediate temperatures, but at low temperatures a description in terms of monopole dynamics alone is insufficient. Recently, numerical simulations were used to argue that magnetic impurities account for this discrepancy by introducing a magnetic equivalent of residual resistance in the system. Here we propose that oxygen deficiency is the leading cause of magnetic impurities in as-grown samples, and we determine the defect structure and magnetism in Y2Ti2O7-δ using diffuse neutron scattering and magnetization measurements. These defects are eliminated by oxygen annealing. The introduction of oxygen vacancies causes Ti4+ to transform to magnetic Ti3+ with quenched orbital magnetism, but the concentration is anomalously low. In the spin-ice material Dy2Ti2O7 we find that the same oxygen-vacancy defects suppress moments on neighbouring rare-earth sites, and that these magnetic distortions dramatically slow down the long-time monopole dynamics at sub-Kelvin temperatures.
Original languageEnglish
Pages (from-to)488-493
Number of pages6
JournalNature Materials
Volume13
Early online date13 Apr 2014
DOIs
Publication statusPublished - May 2014
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

ID: 24208437